If one were to redistribute the unmodified binary installer for the Mozilla Firefox Portable Edition software, whether commercially or non-commercially, would it be necessary to include any additional source files in order to comply with licensing requirements? (Probably not, but the answer is not totally clear.)
As with Mozilla requesting that you direct people to them for downloads rather than mirroring them, it is best to direct people to download from PortableApps.com to ensure they have a legitimate copy of the most recent version. You can redistribute the unaltered installer for Mozilla Firefox, Portable Edition provided you make no alterations to it. Only the digitally signed, unaltered *.paf.exe may be redistributed. It also can not be wrapped in another installer or ZIP file, just the file by itself. You can not charge a fee for redistribution of the software.
Sometimes, the impossible can become possible, if you're awesome!