Open source software is software whose source code is publicly available, with a licence granting the right to study, modify and redistribute it.
Licences
The licence, not the price, defines open source. Two broad families exist:
- Permissive — MIT, Apache 2.0, BSD. Code may be reused almost anywhere, including in closed commercial products, usually with attribution required.
- Copyleft — the GPL family. Derivative works must be released under the same terms, keeping the code open downstream.
Choosing a licence is a strategic decision, because it determines who can build on the project and under what conditions.
Why organisations use it
- no dependence on a single vendor;
- the ability to audit code, which matters for security;
- shared maintenance cost across many users;
- freedom to adapt the software to specific needs.
Where it runs
A large share of modern infrastructure is open source: the Linux operating system, the nginx and Apache web servers, PostgreSQL and MySQL databases, the Python and PHP languages, and the Git version control system. Most of it is invisible to end users but sits behind nearly every website and application.
Risks to manage
Open code is not automatically safe or maintained:
- some widely used libraries are maintained by one or two volunteers;
- an unpatched dependency becomes an entry point for attackers;
- licence obligations, if ignored, create legal exposure;
- "many eyes" does not guarantee that anyone has actually reviewed the code.
Mature organisations therefore keep an inventory of the components they depend on and track their updates and licences.
Contributing
Contribution is not only code. Documentation, translation, precise bug reports and answering questions from new users are all valuable, and are often the areas where projects are short-handed.