Commander Keen was released on May 29, 2001, for the Game Boy Color. Developed by David A. Palmer Productions and published by Activision, it was created as both a sequel and homage to the series as a whole, and does not have an episode number. Id was not a major partner in development, though it retained editorial control over the game, and Adrian Carmack contributed some artwork. The idea for a Game Boy Color Keen game came from John Carmack and id, who approached Activision, which in turn proposed Palmer as the developer.
Source: Wikipedia