So, if I understand this correctly, open source means free beer, just not if you sell the end product.

Yes, once you give the beer to someone, you can't require any further payments no matter what they do with it. Free software philosophy says users are free to use the software however they wish and for whatever purpose they wish without any barriers (like having to pay for commercial use).

its all a scam for free work for corpos then. Very disappointing.

I'm sorry you feel that way, and it's becoming a not-so-rare sentiment lately (or at least I've started noticing it more), but I don't agree. Look at (A)GPL and how many companies are doing their best to avoid such code - like when Google made their own C library for Android and even stated that its main goal was to avoid copyleft licenses. I've also seen plenty of people say that GPL code is pretty much useless for their work due to their company's policies forbidding its use.

I also think that revenue-based loyalties screw over small companies the most - sure, you get the donations from the massive companies that can work with 1% of their revenue gone while also keeping it free for non-commercial users, but in my view you also help those same massive corporations by making the software less viable for their smaller competitors who don't have the economies of scale on their side, and for whom that 1% might legitimately break the bank.

And to be clear, I don't mean any of my arguments as some kind of "gotcha! Look, I'm right and you're wrong", I just thought I might share my reasoning for why I don't think your statement is fair.