If one heads over to GitHub to check some recently closed issues and recent commits one will discover that there are people who can understand and debug LuaJIT issues.
LuaJIT is not magic, it's a software. Very neat and tightly written but it's still just a bunch of C/assembly/Lua code.
Written by one human, and thus other humans can understand it too.
In theory you're right. But it's dense terse code with very little documentation. Some people can fix obvious problems around the edges, but no one would tackle a serious refactoring, porting to more recent version of Lua or adding a new feature.
LuaJIT is not magic, it's a software. Very neat and tightly written but it's still just a bunch of C/assembly/Lua code.
Written by one human, and thus other humans can understand it too.