I agree, he is a very lucky budgie, as he ultimately wouldn’t have survived if not found. I hate to ask, but did you or whoever found him attempt to find an owner? Someone might be missing a sweet little bird.
I second Cody’s opinion on clipping. Although I have a rare exception in one of my parrots. He was born many years ago, and wasn’t really raised properly by the breeder. He was clipped and sold to a bird store before he could fledge. He spent most of his life clipped, so he became accustomed to it and never tried. Now he’s flighted, but won’t fly unless on rare occasion he’s startled. So my opinion is that is a rare exception. If a bird has fledged (able to take first flight) it will most likely always be “in them” to fly. However, for the time being, he will adapt. Birds are very resilient. Helping him with extra perches for now would be nice though.