If you purchase licenses for the app and assign those licenses while the app is free, then I would think that the free license would be honored. When the app goes back to "for a fee", then I would presume that the license would still be assigned and you wouldn't have to pay an additional amount, since the app is already purchased.
I would assume that if the app is updated, that the updates should be included.
Are you seeing something different?
We're not seeing anything different, yet. It's more of a "planning ahead" question. Your take on it is pretty much in synch with me. I was just looking for outside opinions to make sure I wasn't missing anything.
We do grab a lot of free-for-the-day apps and I haven't seen any different than what you described. The only part I wasn't sure if anyone had experience with had to do with the updates. We haven't run into a problem yet there either, but in case it's possible just good information to have ahead of time.