fwiw, I think that subjectively it's roughly equivalent in this specific case. The domain name is a huge part of the brand, and is almost equivalent to the list of prior clients.

I think that it will probably be fine if they compete in the same space of a social network, doesn't look like someone is going to go after them, the company that would have a claim against them is defunct, so even if they have a legal argument, who would raise the case? If the owners do so under their personal name it's even a weaker argument.

So in practice, in this case, subjectively I believe that it's effectively very similar as buying the company.