While the initial function mappings could be quite simple, I see the future of this being a bit like Google Translate for computer languages. We just need a Mechanical Turk wiki like process to get the longer snippets code translated. I used to work with ESRI ArcView software and its Avenue scripting language. When they changed their internal scripting to Visual Basic for Applications, there was a lot of work to be had translating scripts. (Now they support Python as a scripting language as well.) I wonder if for any given JVM language (Java, JRuby, Jython, etc.) you could write a decompiler for the bytecode that would take you back to a different source code language.