I would love to take a look at this; an S3 alternative and open source is a magic combination. Even if it's going to be a one-time product like once.com, I wouldn't mind that at all.
I actually build systems like this for clients for a one-time fee (see UpWork.com link on my GH profile), but all of the set-up instructions are in the repo free of charge. Just be aware even with my notes building one of these things isn't easy