It looks like the bots must be built using BWAPI, an open source API layer for Starcraft that uses ChaosLauncher, an unofficial Starcraft hack. Seeing as how Blizzard is a super litigious bunch of assholes (read up on bnetd [1], WOW Glider [2], and Scapegaming [3] for a sample) won't they just file a baseless lawsuit against the people responsible for this competition? Given their past behavior, I can't imagine that they would be able to restrain themselves.
<rant>
Honestly, Blizzard makes great games, but they have always fought against free speech, intellectual, and technical freedoms. I hope that Starcraft II falls flat on its face for forcing Internet registration to play the single player game [4] and disabling LAN play [5] in the hopes of increasing profit. The sooner that company fails, the better.
</rant>
[1] http://en.wikipedia.org/wiki/Bnetd#Blizzard_takedown_demand_and_lawsuit
[2] http://en.wikipedia.org/wiki/WOWGlider
[3] http://www.rfcexpress.com/lawsuit.asp?id=51340
[4] This has not yet been announced, but it's naive to think that it won't be the case
[5] http://kotaku.com/5304113/no-lan-play-for-starcraft-ii