I would not call it a fork as a fork deviates from original intended operation and in fact often breaks it. In this case, forks usually mine different coins. Forks like VNISH et al kept sha256 mining but have broken the GPL lcense by:
 1. They closed the code so who know what else they have added to it
 2. By closing the code no one else can build on it
 3. They removed all earlier developer and contributor attributions - that is the greatest insult to the original developers & contributors

Long long ago -ck and Kano were the 2 primary developers of cgminer. When -ck dropped further development >5 years ago Kano took over keeping it up to date to use modern chips. If someone wants to contribute useful changes to the code they are welcomed to submit changes to Kano's git for review and possible inclusion into cgminer.

FYI: -ck's 'day job' is a medical doctor (anesthesiologist) - for him coding is a hobby. Kano has always been commercial programmer.