Well, actually...
> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
But from a marketing and sales point of view, it's nowhere.
For example, I can start marketing and selling a new image editor (blimp), and on my web page, in videos, Facebook yo face, I need make no mention that it's based on Gimp.
And that is -explicitly- allowed by Open Source licenses. Which is part of the Ooen Source deal - others can build on what you made, take credit for it, profit from it. That is not a bug, it's a feature which was explicitly allowed for.
You would however, need to make the source code available under the GPL license, since GIMP is licensed with GPL.
I agree entirely :) It's why I prefer to use the MIT / Apache Dual license (and generally to avoid the GPL in certain contexts).
Apache's condition is more explicit and nicer from the attribution perspective
(d) If the Work includes a "NOTICE" text file as part of its
distribution, then any Derivative Works that You distribute must
include a readable copy of the attribution notices contained
within such NOTICE file, excluding those notices that do not
pertain to any part of the Derivative Works, in at least one
of the following places: within a NOTICE text file distributed
as part of the Derivative Works; within the Source form or
documentation, if provided along with the Derivative Works; or,
within a display generated by the Derivative Works, if and
wherever such third-party notices normally appear. The contents
of the NOTICE file are for informational purposes only and
do not modify the License. You may add Your own attribution
notices within Derivative Works that You distribute, alongside
or as an addendum to the NOTICE text from the Work, provided
that such additional attribution notices cannot be construed
as modifying the License.
And at that point you basically can't disagree without looking like a ghoul.