This is a Kinesis Contour 130EM.
This is a quick pic from my phone. hi-res available on request.
Each cup of keys is attached to a rigid (barely flexible) pcboard with six 'fingers' at various curve. The connection to the central board is via one of those exposed Mylar edges that slides into a sleeve which is then clamped shut.
In theory you could split the keyboard with a ribbon cable extension from one or the other fingered pcboard. This is not something I'd want to try, especially if you paid full retail for a Kinesis keyboard, but there are FAR more difficult hacks out there.
I'm curious what you'd use to house the separate pieces after the split?