Thanks for the fast response. I think I have tested other mechanical keyboards with macs and they worked, so it was a surprise.
I was thinking about using key mapping software to solve the issue, but it seems the n-key rollover means the keyboard sends more than one scan code for a single keystroke. I haven't tested it yet, but if this is the case, simple key mapping won't work. Is this documented somewhere? Is it possible to use key mapping to get the keyboard working on a mac?