Joining every TV platform costs money. Also, unlike satellite, Virgin is a closed platform & the whole of their network costs fall on their customers & the channels that join the platform. RT is Free-to-Air on satellite. Apart from the Sky EPG listing they are nothing to do with Sky. They pay a fee to SES (the satellite's owner) to lease a transponder & they can then be available to the whole of Europe if they please for just one fee.
As for Mr Branson. He left the company a while ago now & just leases his brand name. Virgin Media is now a wholly owned subsiduary of the Liberty Global group worldwide cable empire.