Halite also looks interesting, but I think with generals bot-makers will have much more possibilities, because there are no limitations for your implementation. The game mechanics might also a little more challenging in generals, especially the fog of war makes a huge difference imo.

You'd be surprised how many implementation options there are in halite. People have come up with starter packages for just about every language you would ever want to use.

agreed, halite is a well run challenge. The site gives a shoutout to halite: http://dev.generals.io/faq

Unfortunately, the halite challenge is almost over and they will shutdown the site afterwards.