Firefox 55 and the coming Firefox 56 and 57 releases mark an important point in the history of the browser.
Mozilla plans to switch off the Firefox legacy add-on system in Firefox 57 for the bulk of the user base -- those on Stable and Beta versions -- and along with the change come changes to the browser that render some legacy add-ons incompatible already in Firefox 55 and newer.
This is problematic for a number of reasons. First, because legacy add-ons can still be installed and are listed as compatible when you visit the Mozilla AMO website. There is no indication that the add-on fails to work properly as it installs just fine.
Second, if fixes are possible to make the add-on compatible with Firefox 55 and 56 again, but not possible because the author of the add-on has abandoned it.
Earthling, one of the core contributors to the Ghacks Firefox user.js file has fixed the issues in the add-ons. NoRedirect broke because it did not ship with the multiprocessCompatible flag, No Resource URI Leak because it used a related path to load content scripts.
The fixes were straightforward: add the missing flag to the NoRedirect add-on, and change the relative paths of No Resource URI Leak to absolute paths.
While the fixes are straightforward, there is no option for anyone but the original extension author to release the fix on AMO.
It was possible previously to upload a fork to Mozilla AMO to make it available to users who ran into broken add-on issues.
This is no longer possible as Mozilla blocks the uploading of legacy add-ons to AMO.
The blocking of new legacy add-ons removes one core fundamental open source principle from Mozilla AMO: the option to take the source, fork the add-on, and make it available again in a different version.
This applies solely to legacy add-ons, as WebExtensions are not limited in any way. The situation will improve once Firefox 57 gets released so that the bulk of users will have all legacy add-ons disabled automatically.
Nightly users, who may continue to run legacy add-ons will face the issue of broken add-ons however even if a fix would mean to change a single line of code only to make the add-on compatible.
While I can understand Mozilla's reasoning for blocking new legacy add-on uploads to Mozilla AMO, as it could lead to user irritation if a legacy add-on they just installed got disabled when Firefox 57 is launched, it is not the best option to in my opinion.
First, because the same thing can happen with older legacy add-ons that are still offered on Mozilla AMO. Second, because it would have been better if Mozilla would make exemptions for forks of existing add-ons at the very least that fix things.
Now You: What's your take on this?