Open-source licence
The legal terms attached to free software components, which decide whether you may use, change and sell them, and what you must credit or share in return.
Updated October 2026 · with examples from our own builds
What does open-source licence mean in practice?
Most products are built on open-source code, and each component comes with a licence. Permissive licences such as MIT allow almost any use as long as the notice is kept; copyleft licences can require you to share your changes or source under the same terms. Some 'free' tools are open only in part, with key features behind a paywall.
Licences come up at due diligence and whenever you decide to build on someone else's project. The question isn't only 'may we use it?' but 'can we change it freely, and what happens if the maintainer stops?'
Keep a record of the main components and their licences, and keep any required notices in the repository.
Open-source licence at a glance
- Permissive
- MIT and similar: use and change, keep the notice
- Copyleft
- May require sharing your changes or source
- Check also
- How active and well maintained the project is
Where has open-source licence come up in our builds?
Looking for a form builder to stand on in July 2026, we found the free options either kept the builder behind a paywall, added a watermark or came with a copyleft server. We hard-forked the MIT-licensed formeo, run by one maintainer, then deleted its editor and renderer, about 21,500 lines, and wrote our own; the MIT licence notice stays in the repository.
The default narrator is Kokoro, an open-weight 82-million-parameter speech model run on CPU through ONNX Runtime with no per-sentence fee. Music beds play only when licensed tracks are on file, and none ship with the server.
Common questions about open-source licence
Can I use open-source code in a product I sell?
Usually, under permissive licences such as MIT, as long as you keep the licence notice. Copyleft licences may require you to share source, so check each major component before you depend on it.
What is a hard fork, and when does it make sense?
Taking a copy of an open-source project and developing it separately, without tracking the original. It makes sense when the component is central to what you sell and you need full control, at the cost of maintaining it yourself.
Related terms
Sources
Planning a product and not sure where open-source licence fits? Ask us, or browse all 116 terms in the glossary.