i don't know for sure but i would imagine that once the market place is no longer in the beta version they will charge for apps... when that will be... i have no idea.
ehh that would stink if they made you buy the ones you have.
i don't think they can do that... when we got them they were free.... and i don't think they will start charging for them... they will probably only charge for the new apps that are added after the full version of the marketplace
I don't think they're going to take the chance of making their entire user base angry by requiring payment for the apps we already have installed - especially since there was no warning of "will require payment soon" or something. They might already have something in place which shows which apps each person has installed, and then all other apps will revert to "requires payment" after this free period is over, but that's just a guess.