Name: Anonymous 2012-11-11 12:20
Program X is GPL'd. You want to modify it but don't want to release your modifications. Slightly modify the source of X so that it can dynamically load foreign executable code. Have it load your proprietary additions.
Release the source of your Program X fork as GPL, but do not reveal the source of your proprietary additions.
Release the source of your Program X fork as GPL, but do not reveal the source of your proprietary additions.