The blond female pictured on the cover of the Geronimo Jackson album is Karen DeGroot. In DJ Dan's First Live Podcast of August 11, 2006, Dan identified Keith Strutter as the guitarist and founder of Geronimo Jackson, and noted that Strutter's previous band was called The Karma Imperative. During the 7/05 DJ Dan podcast, a man called in, stating that his grandmother had joined "The Karma Imperative" around the 1960's. She was a doctorate at the University of Michigan. One year she apparently ventured with "KARMA", or DHARMA, to a location at the South Pacific called "The Flame".
Geronimo Jackson is a real band, so this is very unlikely.
They are NOT a real band, but the way Cuse and Lindelof keep joking around them is suspicious, and it seems plausible that we will yet find out more about Geronimo Jackson. Why not that they were a band made up of DHARMA members? (evidence for this statement: )