gruk.org is not an ED2K server, it's the place where aMule gets the server list from. But since aMule cannot get its server list from there at the moment, it won't find any ED2K servers either.
I'm not sure whether posting URLs to server lists is desired by the administrators, so please use Google to find one. You need a file called "server.met". Please close aMule, copy your downloaded "server.met" into $HOME/.aMule where $HOME represents your home directory, and then restart aMule.