Is this sold as an assembled programmer?
Not yet, it is only available as a kit
How hard is it to assemble?
There are very clear instructions availble in the "Make it!" link. Its a simple kit and should be fairly easy for anyone with proper tools even if its their first soldering project.
Does this work with linux?
Yes. I have tested it with linux (Ubuntu 7.04) and it didn't require anything strange so it should work with any distribution.
I need help getting this working
Check the HELP! page