Personally, I have no use for double knit in quilts. HOWEVER, I would never refuse a fabric gift from anyone. I'd be afraid that if I refused, the friend would think twice about offering the next time (and the "next time" might be a boatload of 100% cotton). There are many things you could do with this fabric, if you choose not to use it yourself: pass it on to someone that does use double knit; to a church group or local guild that make quilts for Vets, Children's Hospitals and nursing homes.
There's a market out there for this fabric