Years ago I wrote a p2p file sharing program and open-sourced under GPL. Soon a group contacted me for forking the project; I gave them my blessing and wished them luck.

Later I looked at their fork. All they did was adding their names to the copyright and the new project name to the comment section for all the hundreds of files. I was frustrated as this was a clear case of taking copyright ownership for the software. I asked them to remove their names from the copyright unless it's new changes by them but they said GPL allowed it. I contacted FSF for clarification and FSF replied that it's allowed as changing the comment constituted a new change. It's a bunch of BS. It took the rosy glasses off my naive self and soured my view on open sourcing my software in the future.