OpenJJ2?

[Darkhog]

How hard would it be to just rewrite JJ2 engine from scratch? I mean, differences between JJ2 and JJ2+ are so big at this point that it gets harder to implement new stuff when all you have to work with is Win32 debugger. Plus game's quite old and its age shows on newer systems (vide recent DirectDraw issues on Win8/8.1/10).

[Violet CLM]

I mean, differences between JJ2 and JJ2+ are so big at this point that it gets harder to implement new stuff when all you have to work with is Win32 debugger.
Baseless assertion.

Here are the most recent two times people have tried. Neither is currently finished. Both are focusing entirely on SP gameplay for now, because writing network code is a much more specialized skillset and maybe also because an open source multiplayer game feels like a really bad idea.