Trevor Ashfield On Whether Or Not Void Indigo Was The First Repurposed Indy Comic posted November 24, 2012
Scrolling down past all your great gift-giving ideas, I came to your question whether Void Indigo was the first repurposed comic. . . I know of one earlier - the story "Slab' in Eclipse magazine # 1 by Steve Englehart and Marshall Rogers. The story started life as a Superman-Creeper story that Englehart pulled. See his website here.
This was in 1981, beating Void by 3 years. I dunno if it was the first repurposed story -- I'll bet there are stories in Star*Reach that started as something else - but I really have no idea what might be the first. Probably someone in your readership will weigh in with some project that's even earlier!
(Eclipse # 1 really blew my 16-year old mind. . . and the cover really bothered my Mom!)