Mozilla Add-ons has a license link there for every add-on, you cannot submit an add-ons without declaring what license it is. I know there are options to make the source available there, but I don't know the details there, AFAIK I have links in the descriptions of my own add-ons that point to my repos, as the internal option would just display the source in the form it is in the packages.
Unfortunately, this is not the case right now on the Marketplace, and I'd encourage you to file a bug on that (or two, on both aspects). Still, as the apps in the Marketplace are all HTML5, you should be able to just use your browser's "View Source" function to get to that.
Also, how do you think that "open web" means distancing from FLOSS? Both heavily concentrate on open standards and software under free software licenses. Mozilla is pushing heavily for open standards, processes and software, if you have a different impression I'd like to know why and how Mozilla can improve there.