The Foundry range 'licence' was based off a handshake and an email conversation. TWOTS is that Rebellion became aware and let them carry on, but now that Warlord has stumped up the cash for a pukka licence for miniature games based upon the whole of 2000AD, Rebellion have to offer the licensee some protection.
Same thing happened with the BBC, they sent C & D notices once Warlord bought the licence for Doctor Who. Interestingly, it was the BBC who shut the others down, NOT Warlord, who knew the owners of the UK companies and were happy for them to carry on.