IMO, the move from community servers over to matchmaking & vendor only servers being the only viable option was a huge disservice to the long-levity of games. If I find the code around here, I could still get a Tremulous server running today for a few bucks, even if I haven't played that game for 20+ years.
Solutions to this modern problem was solved during the dialup and LAN party era. None of those single player games required an online launcher.
3 is valid and can be tricky, as it would depend on when in the software lifecycle the release would be mandatory. If it's in a wind-down or bankruptcy situation, it would be tricky. Though that discussion is similar to the responsible disclosure discussion, isn't it? Exploiters usually already know them.
Not to mention open sourcing the code will subject the company to legal liability if there’s something weird in there like discrimination of some form.
Thats pretty easy actually.
All you have to do is go into the setting page on the git repo and change the settings from private to public.
I'm sure most game devs are able to figure that one out.
Everything else that resolves was that is merely consequences for which I have little pitty for.