He is most definitely NOT using eMule Plus.
What is happening is that there are some MODs out there that have a setting to do this, namely:
1. They read your nick and identify themselves to you as having the same nick (kind of a copy/paste operation).
2. They read your client software and version and identify themselves to you as having the same client software and version (kind of a copy/paste operation).
These actions are not harmful by themselves, just a little irritating.
Just ignore them as much as you can.
Also, it is not personal; they are doing this to every client they are connected to - showing each of those clients their own nick and client software and version. E.g. if one such client is connected to both you and me, to you he will appear as using your nick, while at the same time to me he will appear as if he is using my nick.