Katana uses LuaJIT quite extensively for user-side OpScripts, and previously both DNeg and MPC (they've largely moved on to newer tech now) had quite a lot of Lua code...
It used to in older (pre 2.0) versions, but due to Python's GIL lock (and the fact Python's quite a bit slower than lua anyway), it was pretty slow an inefficient using Python with AttributeScripts, so 2.0 moved to Lua with OpScripts...
