The main way I know of would be through trademark infringement. That's why there's GNU IceCat/IceWeasel - Firefox contains trademarked material. I believe Mozilla uses trademark precisely to prevent third-parties from including user-unfriendly components in "Firefox".
"By sending or transmitting to us Content, or by posting such Content to any area of the Sites, you grant us and our designees a worldwide, non-exclusive, sub-licensable (through multiple tiers), assignable, royalty-free, perpetual, irrevocable right to link to, reproduce, distribute (through multiple tiers), adapt, create derivative works of, publicly perform, publicly display, digitally perform or otherwise use such Content in any media now known or hereafter developed. You hereby grant the Company permission to display your logo, trademarks and company name on the Sites and in press and other public releases or filings. Further, by submitting Content to the Company, you acknowledge that you have the authority to grant such rights to the Company. PLEASE NOTE THAT YOU RETAIN OWNERSHIP OF ANY COPYRIGHTS, TRADEMARKS AND SERVICE MARKS IN ANY CONTENT YOU SUBMIT."
And this is relevant because ... why? There's no trademark or service mark, and as we've already discussed, the GIMP copyright allows this sort of use.
The permission clause is "You hereby grant the Company permission to display your logo, trademarks and company name on the Sites and in press and other public releases or filings."
This does not appear to include the right to use the trademark in installers, as an installer is neither a site nor press release, etc.
