What we want from our license seems to be all in MPL.

Try reading the annotated version of it:
http://www.mozilla.org/MPL/MPL-1.0-annotated-fs.html

For using the mod library (code) in your own (commercial) program the annotation says:
``Distribution of Executable Versions''
The goal of the NPL and the MozPL is to encourage as much innovation as possible. We anticipate that people will take the code licensed under the NPL and MozPL and combine it with code developed or licensed under other terms. We also anticipate that the combined code will be licensed under a variety of terms, including different payment terms, support terms and use restrictions. Netscape does not wish to dictate the terms under which any such executables will be available. The NPL and MozPL are designed to make sure that the Source Code Modifications are freely available. After that, the creator of a larger work is free to license the executable of the work as he or she sees fit.

See the last sentence.
But if you change something to the mod player you have to make it public. If you just use it as a part of another program it seems to be ok.

Also in the beginning mpl states:
The Initial Developer hereby grants You a world-wide, royalty-free, non-exclusive license, subject to third party intellectual property claims:
Look at the word royalty-free.

So it would be no problem to get the project at sf under mpl1.0 license.