forcing users to give them a worldwide commercial license to everything you enter through Firefox?

That’s not what they actually did, though. They revised the wording to clarify:

You give Mozilla the rights necessary to operate Firefox. This includes processing your data as we describe in the Firefox Privacy Notice. It also includes a nonexclusive, royalty-free, worldwide license for the purpose of doing as you request with the content you input in Firefox. This does not give Mozilla any ownership in that content.

For example, if you type something into the address bar, they need to have the permission to take your content (whatever you’ve typed) and send it to a third party (a search engine) to get autocompletion results.

Here’s the blog post that clarifies the changes: https://blog.mozilla.org/en/products/firefox/update-on-terms-of-use/