Was it free and open source? If it is than I’m not sure how that happed.
Well, first, as people have already pointed our, all GPL requires is that you make the source code along with any modifications you make freely available - you can still sell pre-built versions, and that business can still be sold. You can also own trademarks, logos etc. which aren't an essential part of the GPL's software & can be bought and sold - hence several Linux distributions have a strangely familiar web browser called "IceWeasel" or suchlike.
Secondly, when you release code as GPL you don't give up the copyright - In the case of something like Linux which has a zillion copyright holders, that doesn't amount to much, but if there is a single author - or if the maintainer requires that all contributors assign the copyright to them, then the copyright holder can do what the heck they like with it regardless of the GPL (including releasing modified binary versions without having to open source the new code, or even making the next version closed-source).
Still - once you've released a version under GPL, the source code of that version is irrevocably out there and some other group can pick it up and keep the Free version alive.