That doesn't seem to be the case. From what I read on HN, the dev quit because he thought it didn't make sense to submit CVEs for temporary/wip solutions, and F5 thought otherwise.
So as I see it, the developer quit because he didn't agree that a CVE should be opened for a work-in-progress solution that was live on Nginx.
For the panels issue, you can launch CS2, press Alt+F3 to open the window settings, go to configure special app settings, then set an option for the app so that it always launches in fullscreen mode.
I also added a shortcut to make games fullscreen by pressing Ctrl+Enter.
I believe this is a bug with KDE and should be reported to them. The same issue is reported on Valve's repository but nothing has been done from Valve's side to fix this issue.
EDIT: link for relevant issue: https://github.com/ValveSoftware/csgo-osx-linux/issues/3274
the workaround is written in one of the comments: