As of March 29, 2016, the Firefox Marketplace will no longer support Android, Desktop, Tablets, or payments of any kind (paid apps or in-app payments). Payments are being deactivated, and the Web Runtime is being removed in Firefox 47.
Q. What does it mean for applications already in Firefox Marketplace?
Applications in Marketplace that are compatible with Firefox OS will continue to work on Firefox OS; if they are also compatible with other platforms (like Desktop or Android), then they stop working on those platforms. If the app is not listed as compatible with Firefox OS, it will be disabled (not listed in the catalog), but still accessible to the owner on the developer portal.
Q. What does it mean for new applications submitted to marketplace?
Marketplace will discontinue submission of apps for Desktop, Android, and Tablets on March 29, 2016. It will also remove the Paid Apps options to the submission process. We will continue to review apps submitted for Firefox OS. (We will also discontinue the special submission process for China and for low memory devices, but those changes are already live.)
Q. Why is this happening in March?
This is to give developers time to make changes to their apps while the Firefox release schedule continues once Developer Edition of Firefox 47 is out. (For reference, Firefox 47's timetable is roughly: 2016/01/25 Nightly → 2016/03/07 Aurora → 2016/04/18 Beta → 2016/06/06 Release.)
Q. Where will applications be hosted if marketplace is shut down?
Marketplace is not shutting down. Packaged apps will continue to be hosted on Marketplace and continue to serve Firefox OS users at least until January 2018. Future plans will be reviewed around mid-2017.
Q. If I am a developer with a paid app or have in-app payments in my app, what should I do?
You have several choices: you can make your app free, you can use another payment provider for in-app payments, or you can do nothing -- if you do nothing, your app will be disabled.
To change your app to free, login to the developer portal, select your app, and change your app to free by selecting the Free tab, then the Compatibility tab under the Edit Listing area, and changing it to Free for Firefox OS.