Example: https://addons.mozilla.org/en-US/firefox/addon/homepage-new-tab/?src=userprofile "custom license" points to https://www.mozilla.org/en-US/MPL/MPL-1.1/ and this page is not available. I did hit this problem many times in the past days and as far as I can remember all broken links went to older MPL licenses at very similar urls so it seems that the pages did exist at some point and the links were broken by some site reorganisation.
Thanks for the report - the MPL pages we're recently ported off the old PHP site and onto bedrock. Looks like we may need to update some redirects to fix this.
Created attachment 8686835 [details] [review] pull request
Commits pushed to master at https://github.com/mozilla/bedrock https://github.com/mozilla/bedrock/commit/f31caefcfc54b9bf87ab756d6587745ee57cb2e0 Fix Bug 1216953 - Links to MPL licenses from many addon pages broken https://github.com/mozilla/bedrock/commit/09efaa7628603e4cc23777ed74d702a28bc28b46 Merge pull request #3558 from kyoshino/bug-1216953-mpl-redirects Fix Bug 1216953 - Links to MPL licenses from many addon pages broken