A few months ago I started on a project to make a 'grip' style chording keyboard [0] also based on the teensy, sadly the project has stalled for a bit (graduated and got a full-time).
I have the keys wired [1] but haven't figure out a nice way to mount them yet, and the firmware isn't finished.
[0] http://geekhack.org/index.php?topic=43132 [1] http://i.imgur.com/zQiYmQC.jpg
EDIT: I always found it a bit sad that I was unable to find much documentation on how Engelbart's original chording keyboard worked, does anyone know of a source where I can read how the keys are chorded?