On , I learnt ...

That software can be “free as in mattress”

Extending the notion of “free as in beer” or “free as in speech”, there’s also:

Free as in mattress

This recognises that software is open-sourced when the current maintainers no longer can (or want to) support it. This is akin to leaving an old mattress in the street. It’s free to whomever takes it but is unlikely to be in good condition and won’t be maintained.

Free as in puppy

This recognises that free software can take a lot of work to configure, use and maintain.