Not in the usual sense, because you can still fully fork it, use it, modify it and redistribute it freely like a FOSS software.

You may use or modify the software only for non-commercial purposes such as personal use for research, experiment, and testing for the benefit of public knowledge, personal study, private entertainment, hobby projects, amateur pursuits, or religious observance, all without any anticipated commercial application. You may distribute the software or provide it to others only if you do so free of charge for non-commercial purposes.

The only limitation which make it non-free is :

Notwithstanding the above, you may not remove or obscure any functionality in the software related to payment to the Licensor in any copy you distribute to others.

I don't really understand if it "prevent you" to remove and/or prevent the modification of the donation to FUTO part of the code. Should not prevent you from adding yours on top of it (As in, adding a prompt as in "If you want to do donate to the project, you can donate to the original app owner (DONATE TO FUTO) or the maintainer of the fork you are using (DONATE TO THE MAINTAINER).) And the obvious limitation of making derivative work of it, non-free of course.

Also, they do reserve themselves rights to abrodge the license for those who abridge it, which i don't know how legally useful it may be, for license violations compared to protecting the GPL licenses from violations for example.

tl;dr : Seems FOSS to me, as long as :

• You don't try to make it non-free
• You don't remove the donation to FUTO part of the app