qmail

There is still a difference between copyright and trademark requirements. You can clearly distribute modified versions of Firefox as source code is licensed under MPL. If you make major changes and distribute the end result, you cannot call it Firefox and Firefox makes it easy to do the rebranding. The debate is really about how far should they enforce it and whether it is going to help them preserve the brand. Being too strict will result in forks. Being too lenient will make them lose their trademarks. They have to find a good balance.