I've done some research to see how the ZUG could host the ZSI without killing Michael's server/bandwidth. Two options came up and they both involve ibiblio. ibiblio is the current incarnation of the old sunsite at the university of North Carolina. If you've ever downloaded a file from sourceforge.net you've been presented with mirror choices that include iBiblio.
Checking how-to-submit it looks like the threshold is low -- just make your submissions using the Linux Software Map description format and upload. No muss, no fuss. ibiblio already mirror numerous Linux distributions like Fedora, gentoo.org and others. I think our feed will be accepted as well. The ZUG could still host the ZSI itself but then delegate downloading to ibiblio which automagically mirrors the collection. Sweet!
Another option, perhaps even more radical, would be to move the whole of the ZUG to ibiblio. ibiblio is dedicated to making knowledge available for free. Some sites already hosted there are groklaw.net, the Creative Commons project and others. The collection policy implies the ZUG would be welcome since we compliment the alread existing collection policy for free and open source software. See the FAQ for more information about what's available at ibiblio as far as hosting goes.
Now to be clear I'm not suggesting we consider moving as a reflection on the current ZUG or Michael's stewardship. Both are FANTASTIC!!! I'm just raising the possibility as a way to reduce costs and host the ZUG with other similar projects. I'm also quite content to just host the files from the ZSI at ibiblio or not use it at all. I'm presenting options and extending the dialogue.