What programming languages are being used to build Bitmonerod, Simplewallet, Kovri and the Monero GUI? Are multiple languages used within the same application? What is the level of programming language competency needed to assist with these various projects?
bitmonerod/simplewallet are written in C++, with some C too. C libraries are used (unbound, lmdb, etc). Some C++ bits are pretty intricate. Wallet code is simpler.
Kovri is C++. I've not looked at the code much to say what level is needed.
The GUI is Qt/QML, and C++. I've not looked at it much, but it's way smaller than core, so easier to get to grips with.
Best way to help out is to look for open issues, or something which you find not working, or not working well enough, or not working as you think it should, and go about fixing that issue. Simple things first, and soon you get the hang of it.