I think the important distinction here is that there’s no way to purchase a Virus B/C in a way in which Access see any money from it… so in this regard it’s more like a PlayStation emulator or downloading an old DOS game - it’s probably technically illegal, but there’s no legal route existing by which you could do it (except buying second hand, which doesn’t benefit the company who produced it either).
I guess the situation is a bit muddier because the Ti2 is still for sale which can do the same sounds, the emulation team have said they won’t release an emulator for Ti while it’s still on sale but you could argue people will use the emulator who might otherwise have bought a Ti (and will accept the missing features in exchange for free!).
I can see where you’re coming from. The key difference for me is that you can’t buy a Virus B/C (or software emulation) from Access, so they’re not really missing out on anything (in fact I have a real Indigo bought second hand in storage so I’m probably legally ok!).
But yeah, as the post above says, technically it’s not OK so it’s up to you as an individual if you feel comfortable with it!