The Official Supported languages, since 2005 are LabVIEW, Java, and C++. There are also unofficial languages available including Python, Go, Rust and I'm sure a couple more (generally these run on top of the JRE). This is mainly due to the current controller for the FRC Competition being a National Instruments RoboRIO controller.
For those not in the know, the NI roboRIO is a Xilinx Z-7020 (ARM Cortex-A9 SoC with FPGA) and runs GNU/Linux. As long as your language can target ARMv7 Linux and can call into C libraries, it'll run on the roboRIO.
