Yes, it is true that Chromium is based off of code created by Google, but it
is still considered a lot more open than the non-free Chrome browser.
Chromium is actually less restricive than Firefox as there is no trademarked
graphics or related assets that force the Trisquel teams to alter the code in
order to use it.
You do realize that without Google, that the Mozilla team would lose 90% of
its funding for Firefox. That is why they are starting to push ads and
alternative revenue due to the worry of Google pulling the cord.
Either way, both browsers are backed by Google so if you use either one of
them, you are keeping Google relevant. Sorry to break the news to you.