Sure, but neither Distribution Policy for Mozilla Software[1] nor Mozilla Trademark Guidelines[2] make any mention of the Terms of Use. Services Firefox connects to have their own Terms of Service, like you say, but those are unrealated to Terms of Use for Firefox itself.

[1]: https://www.mozilla.org/en-US/foundation/trademarks/distribu...

[2]: https://www.mozilla.org/en-US/foundation/trademarks/policy/