Now that's tricky seeing as licencing is per household... You'd think they could lock down to several users behind one IP address, but seeing as IPv4 is on its last legs, that falls apart when any ISP is hiding its users behind a pool of IPs!
They have the rights to resell stuff to Netflix (there's a lot of BBC stuff on Netflix US that isn't on UK for example) but couldn't do the same in the UK? I hadn't thought of that angle but I'm surprised if they haven't locked down their rights in the UK. :/
I've got a mate that works for the beeb in production so I'll pester him for his thoughts!
The BBC doesn't sell rights to foreign broadcasters directly, it's done via BBC:WW who buy the rights off the BBC at a commercial rate (often bidding against other distributors, and BBC:WW also distribute ITV content that they've bought it).
The rights for subscription streaming will be very separate to the rights for TVL funded broadcast, and the Iplayer period (which was from memory included as part of the basic broadcast deal hence the limit time, but that took several years to phase in).
In some cases the rights to ongoing streaming for back catalogue content from the BBC may be locked up with a specific service who paid for exclusive rights for a while.
The TVL only ever funds initial broadcasts for a set period (of both time, and showings), and now a limited time on Iplayer.
The contracts to show it on additional non TVL services, or after the TVL iplayer period will be different and require additional payments to various parties.
It's the same reason you used to find some programmes weren't on Iplayer at all, and some programs on other channels might not have been on the +1, the contracts would have stated the channel number of times it could be shown.
Basically the BBC pays for content to broadcast under very specific conditions.
It doesn't pay for the rights in perpetuity or for every possible use, which is pretty much the same as every broadcaster (and that has led to some fun contract renegotiation from what I've heard - including cases of arguments about the definition of "home video" when DVD came out, and then for HD).