Anyone can mirror, but it's a good idea to have:
The greatest risk is that the website will be posted to Slashdot, and the resulting traffic might swamp all of our connections, making them unusable for a time. However, by getting enough mirrors, we can minimise that risk.
A little of your traffic and harddisk space will be used.
If you stop running a mirror, and a bunch of people still try and use you as a mirror, they might annoy you with unwanted traffic or log entries.
Well, fire up your mirroring tool of choice, and tell it to download everything that is in http://nova.yi.org/gnutelladev/ and all subdirectories. Don't follow buttons.
Here is how to do that with wget on a Unix box: wget -q -T60 -nh -nH -L --no-parent -m http://nova.yi.org/gnutelladev/
Send e-mail to TomG at tomg@nova.yi.org, tell him where you've put it, what IP address and what hostname, and which one of those you think is more reliable.