Well as the BBC are so keen to tell (probably better links - but first one to hand - live BBC News at time of writing):
http://www.bbc.co.uk/news/10318089
Don't forget, to watch TV online as it's being broadcast, you still need a TV Licence.
Obviously this is their interpretation - needing a TV Licence even if you don't have a tv and don't watch broadcast tv (assuming you accept broadcast and streamed on the internet are not the same - which seems a reasonable thing to accept).
Perhaps the BBC would argue you need a tv license if you video conference online? Would they still consider it as live TV if the stream was buffered before displaying - 1 second, 5 seconds, 10 seconds etc etc. The limit to their claim is unclear.
The BBC attitude to me is an assault on the internet; and would seem to be an early claim that a license should be required for anyone owning any computer/piece of tech capable of viewing video, is in part why I'd prefer not to support the organisation with my cash.
I should note scrap the license and make the BBC compete and I will gladly pay for anything in which I find suitable value.
What is clear is their interpretation that 'live' requires a license, delayed does not.
For me the value of live BBC certainly wouldn't justify buying license. Given there is no problem accessing the 'catch up' offering without requiring a license it would be nice to be able to have an all in one option to include this (obviously in any case accessible via Wii). If they were subsequently to decide to make the catch up service subject to logging in with license credentials the BBC would still fail to offer value for license fee.
I should note I wouldn't be concerned with live streams from other sources. It would certainly be interesting to see enforcement action being attempted if somebody had say a subscription to Eurosport (or some other website offering streaming media) over internet, no tv, and no evidence of watching live BBC.
What is certain is with the plugin for live BBC and a dedicated media box they would argue a license as needed. Clearly this is easier for them than competing in a free market... A dedicated box and only 'catch up' would seem a tax efficient arrangement.
Sorry for the ramble - I trust reasonably clear.
Just about to post and noticed eddiem's link - that would seem to confirm the above.