The FA offering called PiAware runs a flavour of Debian, called Rasbian. Technically that's the operating system, not a programming language, but that's a nit. If you use the already-prepared image from FA, you don't have to do any programming. It is really simple to get up and running. I'd encourage anyone to give it a try.
The stock antenna that comes with the USB receiver isn't very good. You will likely spend more time making your own antenna from a can and/or copper wire than you will dealing with programming stuff.
In terms of actual languages it is a bit of a mix..
piaware itself is tcl. faup1090 (which converts ADS-B messages to the form that piaware wants) is C. fa-mlat-client is Python with a bit of C. dump1090 (which actually does the work to extract ADS-B messages from the radio data) is C.
But yeah, it's mostly irrelevant if you use the standard image.