How to Filter Open Source Projects by License Type

A license filter is the cheapest legal advice you will ever get. One click on ossium and the GPL projects you can only use under strict conditions disappear, leaving the repos your business can actually build on. Before the click, you need to know what the filter means.

Why the license is a commercial decision. Two open source projects can look identical and have opposite terms. Permissive licenses, MIT, BSD, Apache 2.0, let you use the code in closed, commercial products with light obligations: keep the copyright notice, do not claim you wrote it. Copyleft licenses, GPL, AGPL, LGPL, use the license to force you to share source, and the trigger depends on how you use the software. GPL triggers on distribution. AGPL triggers even if you just run it as a service over a network. If your startup sells software or hosts it for clients, that difference is the difference between a legal cost and no cost. The full explainer has the details: how open source licensing works.

Step 1: Set the license filter on ossium. Open the trending or browse section and apply the license filter before you browse anything. If your product is closed source, filter to permissive licenses only. If you want to see the whole field, leave the filter off, but know what you are looking at. The filter groups projects by license family, so you can go straight to MIT and Apache when your constraint is commercial embeddability.

Step 2: Read the license for the finalists, not the whole field. The filter narrows the list. It does not replace reading the LICENSE file of the two or three projects you are actually considering. Filter metadata can be wrong or missing, so the final check is always the LICENSE file in the repository root and the SPDX identifier on the package page. A minute each, before adoption, not after.

Step 3: Watch the copyleft edge cases. Three that trip people up. First, AGPL: a self-hosted tool you deploy for a client can trigger the source-sharing obligation even if you never distribute binaries. For Indian agencies hosting tools for customers, this is the surprise license. Second, dependency infection: pull a GPL library into an otherwise MIT project and the combined work may need to ship GPL. Third, no license at all: a repo with no LICENSE gives you no rights under copyright law, treat it as read only. Filtering does not catch these by itself, so checking the dependency tree and the absence of a LICENSE file is part of the same pass.

An example. A small Bangalore startup sells a hosted dashboard to Indian retailers. Their constraint is simple: every dependency must allow closed commercial use, and they must be able to deploy instances on client servers without new legal obligations. On ossium they filter trending to permissive licenses, MIT and Apache, and the list immediately excludes the AGPL analytics stack that would have looked perfect otherwise. The license filter did the sorting that a legal review would have done a week later and for a lot more money.

What to check before adopting. Four things, in order. The LICENSE file exists and matches the SPDX identifier. The license is compatible with your distribution model. Your dependency tree contains nothing copyleft that you are not prepared to handle. And the project has a license at all, since "no license" is the one case no filter can fix after the fact.

If you want the broader picture of where license fits into picking a project, the startup selection guide covers the full checklist.