Choosing an open-source license comes down to a single question: how much do you want to control what others can do with your code downstream? If you want maximum adoption and do not mind proprietary reuse, pick a permissive license like MIT or Apache 2.0; if you want improvements to stay open but still allow proprietary use, pick weak copyleft like the LGPL or MPL 2.0; if you want every derivative — and, for hosted software, every service — to stay open, pick strong copyleft like the GPL or AGPL. Everything else is refinement: patent protection, compatibility with the ecosystems you depend on, and how your project earns money.
This article offers general guidance on license selection. It is not legal advice — consult a qualified attorney before finalizing a license for your project.
In practice, MIT and the two-clause BSD license are usually cited as the most permissive open source license options, since they impose almost no conditions on reuse beyond attribution, while the AGPL is typically cited as the most restrictive open source license because it extends copyleft obligations even to hosted, unmodified SaaS use.
The Decision at a Glance
The table below maps common goals to license families.
| Your goal | Recommended license family | Typical choices |
|---|---|---|
| Maximum adoption, allow any reuse including proprietary | Permissive | MIT, BSD, Apache 2.0 |
| Same, but with explicit patent protection | Permissive with patent grant | Apache 2.0 |
| Keep improvements to a library open, allow proprietary use | Weak copyleft | LGPL, MPL 2.0 |
| Keep entire derivative works open when distributed | Strong copyleft | GPL |
| Keep hosted/SaaS derivatives open too | Network copyleft | AGPL |
| Fund a business while sharing source | Copyleft + commercial dual-license | GPL/AGPL with a paid exception |
Most projects that simply want to be used widely land on MIT or Apache 2.0. Projects that want reciprocity — ensuring contributions flow back — choose from the copyleft families depending on how far the reach should extend.
Permissive, Weak Copyleft, or Strong Copyleft?
The choice is fundamentally about the permissive-versus-copyleft trade-off.
Pick permissive (MIT, BSD, Apache 2.0) when adoption is the priority and you are comfortable with others building closed-source products on your code. This is the right call for most libraries, SDKs, and developer tools that benefit from being embedded everywhere. Choose Apache 2.0 over MIT/BSD when you want an explicit patent grant and clear contribution terms — valuable for corporate-backed or patent-sensitive projects.
Pick weak copyleft (LGPL, MPL 2.0) when you want your specific component's improvements to remain open, but you still want commercial software to be able to use it. The LGPL suits libraries meant to be linked into proprietary applications; MPL 2.0 suits code where file-level reciprocity is a natural fit.
Pick strong copyleft (GPL) when you want every distributed derivative to remain free software, and AGPL when you also want to close the SaaS loophole so that hosted, modified versions must share source. These maximize software freedom but reduce commercial adoption, since many companies restrict copyleft in their products. Our concepts library explains the spectrum, and the academy covers how organizations set policy around it.
What Your Choice Means for Contributors, Adopters, and Compliance
A license is a promise to three audiences, and choosing well means thinking about each.
For adopters, the license determines whether they can use your project at all. A permissive license removes friction; a strong-copyleft license will be blocked by many corporate policies. If broad enterprise use is your goal, copyleft narrows your audience.
For contributors, the license shapes the community. Copyleft signals a commitment to keeping the project and its derivatives free, which attracts contributors who value that; permissive signals openness to any use, which attracts a wider but sometimes less reciprocal base.
For compliance and monetization, your choice sets the terms of any dual-licensing strategy. Copyleft is the foundation of the common "open-core" or "sell an exception" model: the project is GPL/AGPL for the community, and paying customers buy a proprietary-use license. Permissive licenses do not support that leverage because anyone can already use the code commercially. Whatever you choose, apply it consistently and record it clearly (a LICENSE file plus SPDX identifiers), because ambiguous licensing is itself a compliance risk. Our comparison pages help you sanity-check compatibility with the ecosystems you build on.
How Safeguard Helps You Track and Enforce Your Choice
Choosing a license is a one-time decision; living with it is continuous. Whether you are the author enforcing your project's terms or a consumer keeping your dependency mix aligned with your product's model, you need visibility into the licenses you actually ship.
Safeguard's Software Composition Analysis resolves the license of every open-source component across your full dependency tree, so you can confirm that everything you depend on is compatible with the license you have chosen for your own project — for example, that a permissive-only product has not quietly pulled in a strong-copyleft package.
SBOM Studio captures each component's license in a CycloneDX or SPDX software bill of materials, giving you an auditable inventory and a clear, machine-readable declaration of your own project's licensing. Policy gates let you encode the rules that follow from your choice — permit compatible licenses, flag or block incompatible ones — and enforce them on every build. Create a free account to map your project's license posture, or read the documentation to set up policy enforcement.
Frequently Asked Questions
What is the best open-source license for maximum adoption? The MIT and Apache 2.0 licenses are the most common choices when adoption is the priority. Both are permissive and allow proprietary reuse, so almost any organization can adopt your code without legal friction. MIT is generally considered the most permissive open source license of the two, since Apache 2.0 adds a few conditions around patent grants and notices. Choose MIT for maximum simplicity, or Apache 2.0 when you also want an explicit patent grant and clearer contribution terms, which many enterprises prefer.
When should I use a copyleft license instead of a permissive one? Choose copyleft when you want improvements and derivatives to stay open source. Use weak copyleft (LGPL, MPL 2.0) when you want the specific component to remain open but still allow proprietary software to use it, and strong copyleft (GPL, AGPL) when you want entire derivative works — or, for the AGPL, hosted services — to remain free. The AGPL is widely regarded as the most restrictive open source license in common use, precisely because it closes the SaaS loophole other copyleft licenses leave open. Copyleft is also the basis for many dual-licensing business models.
Can I change my project's license later? Sometimes, but it can be difficult. If you own all the copyright, you can relicense freely. Once you accept outside contributions, you generally need permission from every contributor to relicense their code, unless you collected a contributor license agreement granting you that right. This is why choosing carefully up front, and using a CLA if you anticipate relicensing, matters.
Do I need a license at all if I just put code on the internet? Yes. Without an explicit license, your code is "all rights reserved" by default under copyright law, meaning others have no legal right to use, modify, or distribute it — the opposite of what most people intend when they publish source publicly. To make a project genuinely open source, you must apply an actual open-source license, typically via a LICENSE file in the repository.