AFAIK the "Touchbook OS" is a beagleboard-ready Angstrom distro with a fancy desktop front-end, if it does get fremantle stuff, it is more likely through cross-pollination via the beagleboard than direct borrowing by Always Innovating.

Personally, I think that without an established company and userbase, it's a bit a of waste to reinvent the desktop/wheel (this trap got OpenMoko to an extent, as well). I guess when they started Mer was way off the roadmap and there are not much many alternatives for an embedded desktop except for the Zaurus descendant they went with in the end. I don't see them being able to carry such a burden for too long so it will leak users to Android and, in time, (depending on progress) Mer.