I'd really _like_ to be able to avoid having to require external executables either, if it can be managed, but that's harder since it means having a pure PHP implementation of the scripting language. (ouch!)
Maybe translating only a subset of JS or Lua to PHP. The engine itself is written in PHP, anyway. Moving to C/Java modules would dramatically reduce the popularity of engine. For example, right now I am having difficulties compiling ffmpeg at old FreeBSD host. I imagine custom php module can have similar difficulties. Dmitriy