Everyone has forgotten it was a Star Wars rip off too, which after 35 years of Star Wars rip offs makes sense I guess.
Sort of a myth, actually. Larson wrote the original screenplay ("Adam's Ark") in the late 60s, about surviving humans (Mormons!) fleeing a dead/dying/war torn/something Earth and heading on a generational ship to Kolob, the human homeworld, under the guidance of the Council of the Twelve. The Cylons were bad aliens or whatever hokum the Mormons buy into.
The only real rip-off element is the idea of manned fighter craft dogfighting in space. One could argue that the show isn't about the space dogfights and, instead, is an interesting take on character-driven journeyman sci-fi and, originally, had more akin, story-telling-wise, to Star Trek, which would have been a major influence on the Adam's Ark script.