See below.
It looks like this is a very simple loader. It writes to SRAM _only_ and then jumps to that program (JTAG loaders typically allow you to write to flash, manipulate registers, and jump anywhere, single step, etc.). Theoretically you could load u-boot this way, but nobody has volunteered that they have done it so you would likely be blazing a new path.
Yeah, and with only 16KB of onboard SRAM, I doubt you'd be able to load U-Boot in as a single image. I don't know if Atmel's host-side DFU app handles downloads larger than the size of SRAM either. So if not, one would have to write an app for that on the host as well.
Having said all that, this is pretty much off topic for u-boot. Only after you get u-boot loaded into the target (and at least showing some signs of life) would this become on topic for this list.
Just out of curiosity, which list would be appropriate then? AT91 Users?
Best Regards,
Joe Grisso Detachment 3 Media, Ltd.