Sorry to bring up an old thread, but I have the exact same question. I've pulled down a Sailfish image for the Nexus 7 and installed it, pulled down the Mer SDK and (following the instructions) have built an image, and have generally exhausted all the documentation that I can find. Now, I want to play around with constructing a UI on top of Mer, and I've reached the same point: the lipstick and lipstick-home source code.

I'm just wondering, before I dive head-first into the code, is there any other documentation I am missing? It just seems to me that the existing Mer Wiki docs describe the SDK and the packaging process in quite a bit of detail, but never actually describe what Mer itself is in any detail...