>No, this project does not intend to supplant the GNU Image Manipulation Program. You may have noticed we already link to their donations page throughout our documentation and we periodically donate a portion of our own funds to the upstream project.

Directly from their FAQ.

There's nothing morally wrong with it at all. On the contrary, the moral argument behind free software is that the work belongs equally to everyone, not to the original authors. There's nothing in the free software ethos that requires "originality" as a prerequisite to redistribute software for any reason, including donations.

The only thing the Gimp authors have a moral claim to is the name and logo.