The site itself is ASP.Net MVC 5 and uses OAuth to allow users to login using their github accounts. The game is displayed live using Signal R. The game engine is a C# library. Bots are written as web servers that respond to a JSON request for a move from the main AI Battleground site. Each contestant is free to program their bot in whatever language they like, as long as they can host it and can respond to requests for a move. My own bot was written in C#.
There are several repositories for different parts of this project that we grouped together into the AI Battleground Organization on Github. The main game engine library is called Bot Wars and my own personal bot from the competition was the GrahamBot.