This season, you can use any programming language you want in FIRST LEGO League.
The Software Section of the Rules mentions the following:
“You can use any software that allows the Robot to move autonomously – meaning it moves on its own. No form of remote control is allowed.”
Please refer to this handy spreadsheet to compare compatible software choices. Please note that while you are allowed to use several programming languages, not all the languages will have equal support for FIRST LEGO League teams.