All hail Stallman & Co and all the brilliant masters of narratives behind them.
There have been occasional examples of misbehavior and ignoring the license terms of certain FOSS licenses, but by and large almost everyone -- including corporations -- does abide by them. The common licenses are well-written, legally solid, and most lawyers (again, and most importantly, including corporate lawyers) agree they would be enforceable in court.
I don't know if you've had a bad experience with releasing free / open source software, and I'm sorry if you have. Many people have seen good results from doing it, and furthermore there's a baseline level of digital freedom now available that is entirely due to people producing such software. The most obvious example, of course, is that you can run a free operating system on your computer and thus not be at the mercy of gigantic tech companies when it comes to privacy, advertising nuisance, non-configurable user interfaces, etc.
It may come as no surprise that I disagree with your characterization of being duped. I'm handsomely rewarded for my work and my resume has never looked better.