This is a followup to this question. To sum: I'm implementing an AI contest site, where each user may submit several AI implementations for different games. Think about Google AI Challenge but instead of just having a big event once a year, I would like it more on a league fashion, with all virtual players playing with each other every some close period of time.

I want to support as many programming languages as possible. I've seen that contest sites (like codeforces) ask you to submit a source code and interact through stdin and stdout. The first question is: what is the best way of supporting multiple languages?

As I see it, I can either ask people to upload some binary/script, and interact either through stdin/*stdout*, or sockets, or the file system; or ask people to submit source code, and wrap it with whatever is necessary for the interaction. I would like to skip the need to compile the code by myself (in the server, I mean), but I am willing to do it if its the "best" choice. I need to comunicate virtual players with each other, or even better, with some intermediary arbiter.

The second question is regarding security. If I'm going to be running user code in my server, I want to ensure strict security conditions, like no file system access, no networking, etc. Otherwise it would be a safe heaven for hackers.

I will be implementing the engine/arbiter in .NET. I would like to support at least C#, C++, Java and Python for the user's implementations. I'm willing to write interfaces for each of these languages to simplify the user interaction with the system.

Thanks in advance.