License Zero Developer’s Guide

License Zero is a game plan for financially sustaining independent work on open software. License Zero lets you make a new deal with users of software you maintain:

Use my software freely for open source or noncommercial work, but otherwise buy a license online to support me.

It’s the model of GitHub, Travis CI, and other leading developer services, adapted for independent library, framework, and tools developers. Finally.

This model also makes it easy to support developers creating open software you use and rely on at work. License Zero is not a donation platform or a backer-rewards market. If other developers’ work helps you do your job better or more efficiently, supporting them through License Zero ought to be a reimbursable expense.

This is a guide to License Zero, the project’s primary documentation for developers. If you’re interested in using License Zero, either to support your work or support others, read this guide. If you find errors or ways to improve it, send a pull request.

This guide describes what License Zero is, and how it works. It is not a substitute for legal advice about whether that system is right for you or your work.’s terms of service apply to this guide, too.


Read This First

def licensing(user, project):
  # See "Public Licenses" below.
  if user.meets_conditions_of(project.public_license):
    # See "Private Licenses" below.
    private_license = user.private_license_for(project)
    if (
      private_license is not None and
    # See "Waivers" below.
      waiver = user.waiver_for(project)
      if (
        waiver is not None and
        not waiver.expired
      # See "" below.
        license_zero.buy_private_license(user, project)

As an independent software developer, you control who can use your software, and under what terms. License Zero licenses give everyone broad permission to use and build with your software, as long as they limit commercial use or share work they build on yours back as open source, depending on the public license terms you choose. Users who can’t meet those conditions need private licenses. sells those users separate, private licenses, on your behalf. A command line interface makes it easy for users to buy all the private licenses they need for a Node.js project at once, with a single credit card transaction. Stripe processes payments directly to an account in your name. The same tool makes it easy for you to sign up, start offering new projects, and set pricing.

This “dual licensing” model is not new. MySQL pioneered it decades ago, and important projects like Qt and MongoDB continue it, successfully, today. License Zero evolves the dual licensing model by making it useful for more kinds of software, and practical for independent developers who can’t or don’t want to set up companies to handle the mechanics of private licensing.

Public Licenses

License Zero starts where you exercise your power as the owner of intellectual property in your work: in your project’s LICENSE file. You might currently use The MIT License, a BSD license, or a similar open source license there now. License Zero offers you two alternatives:

  1. The License Zero Noncommercial Public License (L0‑NC) works a bit like a Creative Commons NonCommercial license, but for software. L0‑NC gives everyone broad permission to use your software, but limits commercial use to a short trial period of 32 days. When a commercial user’s trial runs out, they need to buy a private license or stop using your software.

  2. The License Zero Reciprocal Public License (L0‑R) works a bit like AGPL, but requires users to release more of their own code, in more situations. L0‑R requires users who change, build on, or use your work to create software to release that software as open source, too. If users can’t or won’t release their work, they need to buy a private license that allows use without sharing back.

Both L0 public licenses are short and readable. You should read them.

Comparing Public Licenses

The two License Zero public licenses aren’t just worded differently. They achieve different results. Abstracting them a bit:

def noncommercial_license:
  if commercial_user:
    if within_trial_period:
      return 'free to use'
      return 'need to buy a private license'
    return 'free to use'

def reciprocal_license:
  if building_software:
    if release_software_as_open_source:
      return 'free to use'
      return 'need to buy a private license'
    return 'free to use'

Consider a few user scenarios, and how they play out under different License Zero public licenses:

  1. A developer employed at a for-profit company wants to use a License Zero library in their company’s proprietary web app.

  2. A developer employed at a for-profit company wants to use a License Zero library in the data synchronization software their company ships with voice recorders. They plan to release the sync software as open source.

  3. A developer employed at a for-profit company wants to use a License Zero video player application to show commercials in their office lobby.

L0‑NC allows users to build and use closed and proprietary software with your work, as long they use it for noncommercial purposes. L0‑R allows users to build and use only open source software with your work, even for very profit-driven purposes. Many noncommercial software users are happy to make their work open source, but many make closed software, too. Many for-profit companies make closed software, but many also make and release open source software, too.

License Zero was inspired by imbalances in the relationship between open source developers and users. Both License Zero public licenses represent new deals between developers and users, designed to redress that imbalance. It isn’t clear yet which public license approach is best, either overall or for any particular kind of software. Before you pick a public license, make a few notes about how you think users will use and build on your software. Then think about how they will play out under L0‑NC, and then again under L0‑R.

A key consideration for applications is whether you want to require users to buy private licenses for commercial use. Say you write an image manipulation program. L0‑R would allow anyone to use your program for any purpose, including commercial purposes, so long as they don’t modify your program or build on it to make closed source. That’s unlikely for an image manipulation program, as opposed to a software library or a software development tool. On the other hand, L0‑NC would require users to buy a private license after 32 days.

License Politics

The differences between the public licenses, especially on commercial use, reflect some political differences that you should be aware of.

L0‑NC is not an “open source” or “free software” license as many community members define those terms, because it discriminates against commercial use. Source for L0‑NC can still be published and developed online, using many popular services like GitHub and npm. But many in those communities will not accept it as part of their movements, and perhaps criticize you for referring to it as “open source” or “free software”.

L0‑R, on the other hand, was written to conform to the Open Source Definition, and proposed to the Open Source Initiative’s license-review mailing list for approval in September of 2017. Approval has been controversial, in part because L0‑R goes further than existing licenses in when and what code it requires be released as open source. It’s our position that L0‑R conforms to the Open Source Definition as written, resembles licenses that OSI has approved in the past, and that software under L0‑R is therefore open source software.

L0‑R is probably not a “free software” license as defined by the Free Software Foundation. FSF’s definition of free software requires granting freedoms to run, copy, distribute, study, change and improve software. But it also recognizes that some conditions on those freedoms can enhance software freedom overall by ensuring that others receive source code and freedom to work with it. However, FSF’s definition of free software admits only conditions on the freedom to share modified versions with others, not other freedoms. That partially explains why the Open Source Initiative approved RPL‑1.5, a thematic predecessor of L0‑R, while FSF considers RPL non-free.

In the end, your software is yours to license. These politics may or may not matter to you, and they may or may not matter to your users or potential users.

Private Licenses

Users who can’t meet the conditions of the License Zero public license for a project can buy a private license that allows them to use the project without meeting those conditions. License Zero publishes a form private license, and sells private licenses to uses on developers’ behalf.

Each private license grants the buyer broad permission under copyright and patent law to use the software, in language a bit more like what a company legal department would expect. Otherwise, the legal effect is much like that of a permissive public license, except the private license applies only to the person who bought it, from the date they bought it.

Private licenses give the buyer limited ability to pass their licenses on, or sublicense, others. Generally speaking, buyers can pass their licensees on to others if they build software with significant additional functionality with the License Zero code. They can pass on only the right to use the License Zero as part of the new program they’ve created, and to maintain it. They can’t pass on their license build different programs with the software. In other words, buyers can sublicense the “user” parts of their private licenses, but not the “developer” part of their private licenses. Other developers who want to develop new programs, commercially or as closed source, need to buy their own private licenses.

Private licenses last forever, and cover all contributions that the developer makes with the same project identifier listed in the private license. Developers don’t promise to do any new work, or make it available under the same project identifier, by selling private licenses.


Waivers work a bit like freebie private licenses. Developers can use the command line interface to generate signed waivers for specific people that let them out of public license conditions limiting commercial use or requiri open source release. Developers can generate waivers that last only a set number of days, or that last forever. The command line interface treats waivers just like private licenses for purposes of quoting licenses a users needs for a project.

You might like to issue waivers to reward contributors to your project who make their work available under a permissive license, for parallel licensing, extend the free trial period for projects under L‑NC terms, or to resolve a question about whether a particular use will trigger the commercial-use time limit.


License Zero allows developers to set a price for changing the public license terms for their contributions to a project to those of The License Zero Permissive Public License (L0‑P). This is called “relicensing”.

Permissive License

L0‑P is a highly permissive open source software license, much like The MIT License and the two-clause BSD license, but easier to read and more legally complete. It gives everyone who receives a copy of your software permission under copyright and patent law to work with and built on it in any way they like, as long as they preserve your license information in copies they give to others and refrain from suing users of your project for violating patents on it.

Relicensing contributions to a project under L0‑P removes any reason for users to purchase private licenses for those contributions. Under the agency terms that developers must agree to in order to offer private licenses through License Zero, they must retract a project for sale through the API if they relicense it.

Relicense Agreement

The relicense agreement sets out the terms of agreement between a contributor and a sponsor paying to relicense their contributions. When a sponsor pays the price, Artless Devices signs the relicense agreement with the sponsor on the contributor’s behalf, as their agent.

The contributor’s obligations are set out in the “Relicensing” section of the agreement. Once the contributor receives payment, they’re obligated to take the steps listed there. is a website and API for selling private licenses, closing relicense deals, and generating waivers.

You can think of as a kind of Internet vending machine. As a contributor, you can make a deal with the operator of the vending machine to stock it with private licenses and relicense deals for sale. The vending machine then handles taking payment and issuing licenses on your behalf.

You could also think of as a kind of e-commerce platform service-izing the back-office operations of a dual licensing business:negotiation, communication, payment processing, records management. Rather than start a company and hire to handle those tasks, or take time away from development to do them yourself, you can use to run your licensing business. It works just a well for expensive licenses priced in the thousands of dollars and relatively cheap licenses costing just a few bucks.

Stripe Connect

You can create an account to sell private licenses through License Zero by linking a standard Stripe payment processing account, via Stripe Connect. Stripe Connect enables License Zero to connect its Stripe account to yours, then generate access keys to initiate payment processing requests directly on your account. Stripe assesses its fee, and any commission for, on the transaction.

Identifiers generates unique identifiers for each developer and each project. The identifiers are version 4 UUIDs like:



When you connect a Stripe account to, the site creates a unique UUID for you, as well as a NaCl/libsodium style Ed25519 cryptographic signing keypair. signs most kind of licensing information, from package metadata to LICENSE files, private licenses, waivers, and relicensing agreements, with the keypair created for your account, as well as its own keypair. publishes the public signing key generated for you on your project pages, and via the API. Users can leverage the command line interface to verify signatures on private licenses and other documents against the public key. will not share the secret signing key generated for you with anyone, even with you. But using the API, through the command line interface, you can have sign waivers and package metadata on your behalf.

Project Pages serves a page with project information and purchase forms for each project. For example:

The URL pattern is:{UUID}

Where {UUID} is the UUIDv4 for your project.

Pricing Graphics serves SVG graphics with private-license pricing information that you can include in your project’s README file or other documentation. For example:

a pricing graphic

The URL pattern is:{UUID}/badge.svg

Where {UUID} is the UUIDv4 for your project.

The Markdown syntax is:


Artless Devices

Artless Devices LLC is a California limited liability company. It serves as the legal counterpart to those technical systems. As a maintainer, you will have three legal relationships with Artless Devices:

Service Provider

To use and its API, you must agree to terms of service with Artless Devices. The terms were written to be read, and you should read them. They set important rules about responsibility and liability, and make very explicit that Artless Devices isn’t going to provide, or be responsible for, any legal advice about whether License Zero is right for you or your project.

Licensing Agent

To offer private licenses for sale through, you agree to the agency terms with Artless Devices. You should definitely read that agreement, and again, it was written to be read, not to glaze your eyes over. But there are a few especially important aspects, from Artless Devices’ point of view.

First and foremost, you appoint Artless Devices as your agent to sign license agreements, waivers, and relicense agreements on your behalf. That means that Artless Devices can do the deals you authorize through the API, via, with the same effect as if you’d signed them yourself.

Second, Artless Devices earns commission on private license sales. The amount is set out in the agency terms when you offer the project for private licensing.

Third, you guarantee that you have the rights to offer the software you offer to license through License Zero, and to keep your project’s metadata in line with what the command line interface generates. The guarantee helps protect Artless Devices from those trying to take license fees for others’ work. Your promise about metadata helps ensure that the command line interface works as intended for users buying licenses.

Fourth, the relationship isn’t exclusive, and either side can end it at any time. You can sell private licenses through other services, or on your own.

Finally, neither the terms of service nor the agency terms change ownership of any intellectual property in your projects. You own your rights, and you keep them. Artless Devices doesn’t receive a license from you and license users. Rather, you license users and agree to relicense projects directly. Artless Devices merely acts as your agent, signing on your behalf, as you’ve directed.


Artless Devices owns and licenses the intellectual property in the command line interface that you will use to register and offer licenses for sale, as well as forms and other software tools published online.

Command Line Interface

The command line interface is the primary way developers interact with

With Node.js and npm installed, you can install the CLI with:

npm install --global licensezero
licensezero --help

You can also run the latest version of the licensezero command using npx:

npx licensezero --help

Identify Yourself

To use the CLI as a contributor, user, or both, first run licensezero identify:

l0 identify "Jane Dev" US-CA

Provide your exact legal name, an ISO 3166-2 code for your tax jurisdiction, and your e-mail address.

A few example tax jurisdictions:

As a Contributor


To offer private licenses for sale via, you need to identify yourself with licensezero identify, then register as a licensor and connect a standard Stripe account:

l0 register

l0 register will open a page in your browser where you can log into Stripe, or create an account and connect it. Once you’ve connected a Stripe account, will provide you a licensor identifier and an access token that you can use to create a licensor profile:

l0 set-licensor-id $LICENSOR_ID

The command will then prompt for your access token, and save it for future use.

Offering Private Licenses

To offer private licenses for a project:

cd node-project
l0 offer --private 300

If you like, you can also set a relicensing price:

licensezero offer 50  --relicense 200000

You can run the reprice subcommand to update pricing.

Once you’ve registered the project, use the CLI to set licensing metadata and LICENSE:

licensezero license $PROJECT_ID --noncommercial
# or
licensezero license $PROJECT_ID --reciprocal
git add package.json LICENSE
git commit -m "License Zero"
git push

These commands will write a cryptographically signed LICENSE file, and plus license and licensezero properties in package.json. The additions to package.json allow the CLI to identify the package for users quoting and buying private licenses.


By default, you can change pricing for private licenses at any time. You could offer private licenses for $5 today, and $5,000 tomorrow.

In order to provide a publicly verifiable guarantee of license availability and pricing, either to users or others who want to build on your work, you can lock private-license pricing for your project to no more than the current price for a term of days, months, or even years.

licensezero lock $PROJECT_ID $UNLOCK_DATE

The unlock date must be a date at least seven calendar days in the future.

Locking a project prevents you from increasing pricing for your project or withdrawing your offer of private licenses. For specifics, see the agency terms.

Please note that locks are irrevocable. Artless Devices will not unlock a project early under any circumstances.

Generating Waivers

To generate a waiver for a project, provide a legal name, a jurisdiction code, and either a term in calendar days or forever:

l0 waive $PRODUCT_ID --name "Eve Able" --jurisdiction US-NY --term 90 > waiver.json

You can also issue waivers that don’t expire:

l0 waive $PRODUCT_ID --name "Eve Able" --jurisdiction US-NY --days forever > waiver.json

Retracting Projects

You can stop offering private licenses through at any time:

licensezero retract $PROJECT_ID

Please note that under the agency terms, Artless Devices can complete private license and relicensing transactions that began before you retracted the project, but can’t start new transactions.

As a User

Quoting and Buying

You can generate quotes for License Zero software within the node_modules directories of your projects:

cd node-project
l0 quote

To buy missing licenses for dependencies of a project:

cd node-project
l0 buy

l0 buy will open a webpage in your browser listing the licenses to buy and taking credit card payment. On successful purchase, will provide the address of a purchase bundle that you can use to import all of the licenses you’ve just purchased at once:

l0 import-bundle{code}

Importing Waivers

To import a waiver:

l0 import-waiver waiver.json

The command will open a page in your browser where you can log into Stripe or create an account, then link that account to Once you’ve successfully linked your account, you’ll receive an identifier and an access token that you can save with:

Sponsoring Projects

To sponsor relicensing of a project onto permissive terms:

l0 sponsor $PROJECT_ID

The command will open a payment page in your web browser.


As a independent software maintainer, you can license your work under both a public license and private licenses at the same time because you own the intellectual property in your work that others needs licenses for. In other words, you can dual license your work because you own it.

When others contribute to your work, they will own the intellectual property in their contributions, not you. As a result, users of your combined work will need licenses from you and from other contributors. There are two straightforward ways to achieve that.

Parallel Licensing

You can choose to take contributions to your project only from those who license their contributions under permissive open source terms. For example, you might license your work on a project under L0‑R, but ask contributors to license their work under L0‑P, and append the text of that license to your project’s LICENSE file with a note that others’ contributions come under that license.

Users of the combined project would then receive a license from you on the terms of L0‑R, for your contributions, and licenses from other contributors on the terms of L0‑P, for their contributions. Would-be users who won’t abide by the open source release conditions of your license can still buy a private license from you, for your contributions. The private license for your work, plus the permissive license for others’ contributions, cover all contributions.

In that kind of situation, you can sell private licenses for your contributions to the project, but others cannot. Perhaps that feels completely fair. If it doesn’t, you may like to offer special credit, payment, or a free waiver to contributors, to convince them to license their contributions under permissive terms.

Stacked Licensing

License Zero also supports projects that require multiple private licenses. If you publish a project under L0‑R, and another developer forks the project, licensing their own work under L0‑R, too, they can append package.json metadata for a separate License Zero “project” in the same software. Users who run the command line interface will see that they need a private license from each of you to use the project. The same could happen with two contributors using L0‑NC, or contributors using a mix of License Zero licenses.

Note that as a contributor, you control pricing only for your own contributions, not anyone else’s contributions, even if their work builds on yours. Contributors building on top of work you license under L0‑NC will need to purchase private licenses from you to use and build on your work for the purpose of making money through License Zero, but otherwise, License Zero doesn’t say anything about any relationship between you.

Complementary Approaches

License Zero isn’t the only way to financially support your work on open software, and it tries its best to remain compatible with other opportunities.