Looks like LuaJIT is really going to fork away from Lua this time. After these changes, it won't be a compatible Lua 5.1 implementation anymore, it will be a new language.
So shouldn't it have a new name?
well, it doesn’t say Lua5.1-JIT
It could be opt in.
Are there any rough estimates on popularity of lua implementations? At this point it feels lua means luajit
Why won't it be compatible? Any code written in Lua 5.1 will run on LuaJIT.