It is probably more like 10k+ players or so that play EQEmu, considering that many days the total peaks around 1k, and that is only a portion of the total active players who just happen to be on at that time. Here is the server list that shows the totals for each server and the total for all servers combined:
http://www.eqemulator.net/index.php?pageid=serverlist
Also, the reason Sony doesn't stop the project is because we make sure not to break laws that would let them stop it. Our project is software that has been developed completely independently from SOE by the EQEmu Devs over the years. All it does is run the server-side of the connection, which is something SOE has never distributed. We do not distribute the client, only the server and it's source code that was developed by us.
It is against the SOE EULA to play on EQEmu servers as far as I know, but there should be little concern of being banned for doing so unless you are talking about it openly on EQLive often. Playing EQEmu is not illegal unless you acquired your client files illegally instead of buying the game like you are supposed to. Running a server is not illegal unless you are breaking certain laws while doing so. Really, I don't think SOE cares to spend the fees to take anyone to court over such a small player-base anymore. Plus, I am pretty sure they visit here and get ideas of what they can do with EQLive to make new content and features by copying what we have done. Many people that play EQEmu do it because they don't want to pay to play. So, SOE is probably not losing much money by allowing the projects to exist, and they may even get a little benefit from it.