I can be wrong but these are what I know about MPL:
You can sell your program and make it closed-souce, but
- You have to mentioned the libraries you used if they're in MPL license
- You can't change the license of those MPL-licensed libraries, you must mentioned that they're in MPL and you must give them proper credit (the author, library name, website, download link, etc)
- You must include the license file of the MPL-licensed libraries you used, in your distribution
- If you modified/improve the MPL-licensed source code, you must clearly mentioned what changes you've made on them