May not be minimal to maintain and patch legacy C++ code against various security vulnerabilities. The risk/benefit of doing imperfect patching might obviously indicate shutting it down.
Meanwhile, open-sourcing is usually inhibited by 1) licenses of middleware in the tech stack and 2) sketchy code that's not ready for public sharing. It truly is a ton of work to open source commercial code!
If they opensource the older server code, someone else can build a new compatible version with say, golang or rust, that can end up leaner & faster but also a bit more secure as it can be updated.
I’m sure that’s a big consideration, but they really could just dump whatever code they own the rights to, in whatever state it’s in, and people would be thrilled.
Although, now that I write that out, I bet determining the code they have rights to is, sadly, more work than they’re willing to put in.
Edit: also, if some of the code is used elsewhere in current games, this could inadvertently reveal security bugs in them.
Meanwhile, open-sourcing is usually inhibited by 1) licenses of middleware in the tech stack and 2) sketchy code that's not ready for public sharing. It truly is a ton of work to open source commercial code!