Reference material on individual publishing platforms, grouped by what they are rather than who makes them.
The distinction that matters most in practice is not open source against commercial, but whether you can get at the underlying data. A self-hosted system with a database gives you everything. A hosted builder gives you whatever it chooses to export, which is often less than you expect.
Where to start
The platform index lists every system covered here, split into content management systems, forum software, and hosted or desktop builders.
If you are trying to work out what an unfamiliar site is built on, identifying a CMS covers the checks that work.