Licenses don't expire (other than the shortly used rented licenses), only member area expires; you can renew your member area access for $99/yr or upgrade to gold; I think gold from silver is only like $200 or something, i am not entirely sure there.
As is, I think the only "trial" available is the UBB.Threads7 and thats hosted locally on the UBBCentral servers vs downloadable.
UBB.T7 should run just about anywhere you could want to put it... Uses only standard modules that ship with PHP/MySQL up to the latest versions I believe (though the latest build of MySQL has a quirk iirc).
