We've been collaborating on some points - they actively watch our bugtracker, and we watch theirs (to some degree ). Personally, I think the goals might be different - from my pespective they seem to work on a lot of devices and offer a lot of choice, while our goal is "more simple" (in some sense), we want to offer the Maemo experience, first on the N900, and then on some other devices.

Additionally, I'm personally not satisfied with older vendor kernels, so I'd really want to push for a 'mainline only' (or very close to) policy. I believe postmarketOS is also pushing for this, but they (AFAIK, could be wrong) also ship various devices with Android kernels, I believe.

But others know more about pmOS. Both projects exist, and I think it's important that we collaborate. But don't expect Maemo Leste to switch to KDE plasma any time soon, so to say.