I would seriously consider updating to 10.3 -- you're machine will become *much* faster.
If this is absolutely not an option you can try if mldonkey still runs on 10.1. Back in those days that was the only ed2k client available for the Mac and it ran fine under 10.1. You could also try the official eDonkey client, but honestly, that's just a piece of crap. Given that youre machine is running 10.1, it has to be at least 3 years old. On a machine like that eDonkey will probably consume about 60-70% of your CPU (that is, if it runs at all).