I have received and email about two open source Gomoku programs from Dzon Korniszon.
First program is Carbon Gomoku on GitHub. We tried to port it to Gomocup AI and it appears that Carbon Gomoku is quite strong. Petr Lastovicka is working on Carbon Gomoku port for Gomocup.
The second interesting AI is Stahlfaust Gomoku AI player on github. This AI is under GNU General Public License, so it can be ported if someone is interested.