Probably, but honestly servers are sort of in the same boat.

I think Blizzard hasn't bothered going against the open source servers because even if there's just a 1% risk that a court would rule agains them, it would open the flood gates to much more professional teams to come in and do it because "it's legal".

They do go against server operators sometimes, though they don't seem very determined there, and some servers have resisted successfully (hosting in Russia and identity hiding I think). I think they mostly use "you're using copyrighted assets" as a line of attack, precisely to avoid the risk that losing that would put them at risk. But IANAL.

Also note that in both cases the projects need the assets from a real client and don't ship with them, expecting you to provide them.