I would probably go with a client server approach using TCP. The main game, the arena, will be the server and will wait for bots to connect as clients. This should allow for all the Pascal dialects to be used on all platforms. You could then add a template for TCP communication for the most popular languages (FPC, Delphi and Oxygene) to make it easier for developers to focus on the ai.

We talked a bit about this form of competition a while ago in the next PGD Challenge thread. Some of us were interested and some were not. Personally I find ai interesting and would be up for such a competition. If there is enough interest in it, I may try and create a simple ai game this summer which we can use for such a competition.