"We've deployed your installation with a provisional, expiring license. We'll issue your permanent license once you've confirmed the software is installed and configured to your liking."
Then when they send the check, we send the license. It's never been a problem for any of the parties because we've always been very up front about how the process works. No surprises.
I sold a piece of software to a local business a few months ago that works on expiring dates. Each payment I get from the owner pushes back the expiration date until I get the full amount, at which point it's theirs forever(it's worth mentioning that so far things are great).
We didn't agree to a contract for the work I did, so I can only hope I don't get screwed over some how in the future. It was my first freelance job though, so I guess there's a lesson to be learned.
So, a free tool has a provisional, expiring license. I think this is kind of bull, personally. Especially given that we pay a 5 figure support contract in an effort to support dev efforts on the product. We generate minimal support requests.
I recently found a bug in their product, their first line of support couldn't figure it out even though I sent them a detailed explanation along with a pointer to their source code where the fix should be. Maybe next year, I'll just fix my own bugs and not bother with the support contract . . .
GPL version with no support. NON-GPL version with support.
This is a widely used method for monetizing own projects with enterprises as they feel safer using NON-GPL apps/code for perceived legal issues.