When you upload or input information through Firefox, you hereby grant us a nonexclusive, royalty-free, worldwide license to use that information to help you navigate, experience, and interact with online content as you indicate with your use of Firefox.

I'm trying to parse this. If you take the basic bits, they're saying they can do anything with the info you give them.

When you upload or input information through Firefox (anything you do), , you hereby grant us a nonexclusive, royalty-free, worldwide license to use that information.

The rest is just justification for the first part. They basically can use it in anyway they see fit.

Do these rights apply to forks?

Edit: These are the 2 I'm concerned about in the Acceptable Use policy:

• Violate the copyright, trademark, patent, or other intellectual property rights of others,
• Violate any person’s rights of privacy or publicity,

That means corporations can go after you for either.