Interpretation of Java or Ruby neccessary with every access?
No. Bytecode caches are available for PHP (e.g. Zend Accelerator); Java is compiled to bytecode. Can't speak for Python.
JavaScript on the server can be interpreted to mashine code using Google's V8 Javascript Engine. But PHP and Ruby and Python and Java all have to run through an interpreter every time they're accessed and it interpretation will be less fast.
Is that true? I read this in an article about Google's V8 Javascript Engine.