If it has been washed and dried, and the selvage is the same "size" as the rest of the fabric - In an absolute pinch I would use it. If I was worried about more shrinkage, I would clip the selvage at intervals up to the seam line. (And then put fray-check on the clipped spots.)
The "however" part - the selvage is usually more tightly woven than the rest of the fabric and sometimes might be a bit of an issue when it comes to the quilting part.