Yes, you are right. This is from their trademark site:
Modifications
If you're taking full advantage of the open-source nature of Mozilla's
products and making significant functional changes, you may not redistribute
the fruits of your labor under any Mozilla trademark, without Mozilla's prior
written consent. For example, if the product you've modified is Firefox, you
may not use Mozilla or Firefox, in whole or in part, in its name. Also, it
would be inappropriate for you to say "based on Mozilla Firefox". Instead, in
the interest of complete accuracy, you could describe your executables as
"based on Mozilla technology", or "incorporating Mozilla source code." In
addition, you may want to read the discussion on the "Powered by Mozilla"
logo.
In addition, if you compile a modified version, as discussed above, with
branding enabled (the default in our source code is branding disabled), you
will require Mozilla's prior written permission. If it's not the unmodified
installer package from www.mozilla.com, and you want to use our trademark(s),
our review and approval of your modifications is required. You also must
change the name of the executable so as to reduce the chance that a user of
the modified software will be misled into believing it to be a native Mozilla
product.
Again, any modification to the Mozilla product, including adding to,
modifying in any way, or deleting content from the files included with an
installer, file location changes, added code, modification of any source
files including additions and deletions, etc., will require our permission if
you want to use the Mozilla Marks. If you have any doubt, just ask us at
[email protected].
