Unfortunately, Yahoo's hybrid maps work like Google's in that they combine two separate images (a satellite image with a road overlay) on-the-fly, directly on the web page, and as such, there is no single repository that stores the hybrid maps.

In order for Maemo Mapper to use hybrids maps from Google or Yahoo, it would need to be changed to support the concept of multiple simultaneous repositories overlaid on top of one another. It will definitely affect performance in a negative way, but 've been planning to implement it for a while now; I just haven't had the time. Until that happens, though, Maemo Mapper cannot support Google's or Yahoo's hybrid maps. Sorry. :-/