Program in C, Python, other languages ?
If you want to program the Barionet in other languages than Lua, this is perfectly possible but we will only provide limited support to the effort as we have picked Lua as the main, offically supported programming environment.
Python
OpenWRT (the operating system running on the Barionet) fully supports python, there are all necessary support packages and the interpreter available for both version 2.7 and 3. Using the package manager (opkg) you can install whatever you deem necessary. Note, however, that the Barionet memory is quite limited.
C
C programming is possible and efficient. The compiler can not really run on the Barionet, you probably will need to set up a development server for cross compilation. Big project ? We will support you.