There’s one more thing to consider: CloudMade developer community has a lot of talented people in it that could help with the development of the library, but so far Web Maps API was not a part of our open source efforts.
Leaflet is built from the ground up to work efficiently and smoothly on both platforms. It’s very fast, lightweight while still having a strong browser support, and really easy to use. It also has a clean, simple and readable OOP-based code, and it’s hosted on the world’s best open source collaboration platform — GitHub, so contributing is a snap.
It’s still in the beta stage of development, so it lacks a couple of features and has some rough edges, but it’s moving fast — try it and give us some feedback, either by tweeting to @LeafletJS or reporting bugs and discussing features on the issues page.
Find out more on the Leaflet official website.