From the XFree-Local-multi-user-HOWTO (http://www.tldp.org):

You can have multiple independent graphic cards and multiple independent mouses, but in order for multiple users to interact with the system, they do need independent keyboards as well. Multiple independent keyboards is the feature that linux-2.4 (and in the future linux-2.6) lacks, and this is what Backstreet Ruby adds to the stable Linux kernel linux-2.4.

I wonder if that means I can get keyboard-specific maps…