[N3WBI3]

you would only have to license your modifications to the Mozilla code under the MPL. Your own code can remain proprietary.

Souds a bit like the LGPL..

[antiRepublicrat]

Souds a bit like the LGPL..

Sort of on the subject of module additions to MPL code, but it's a lot clearer, and does it the other way (MPL code as a core part of your application).