LuaJIT is written with security in mind. LuaJIT 2.x had permanent write-protection enabled for the generated machine code in the first release, i.e. before anyone else did so.

I do not see how maintainability could somehow have an inverse relation to the engine speed. IMHO the LuaJIT code base is significantly more maintainable than the Mozilla code base.

Related: Fate of Unladen Swallow and TraceMonkey predicted about two years ago, in February 2010: http://www.reddit.com/r/programming/comments/azibq/a_rant_ab...