Comment by weinzierl

Free and open source is necessary but not sufficient to protect you from the bait and switch (or general lock-in).

You need at least:

1. A Copyleft license

2. Rights staying with the authors, no CLA, no Copyright assignment

3. A diverse enough set of truly independent contributors to reliably prevent collusion.

Bonus points if everything is held together by an organization that operates for the good of the public (and not only its members, 501(c)(3) > 501(c)(6)).

Good examples are Linux, Git, Inkscspe and QEMU. Notably all software from the 90s or early 2000s.