In my academic area I constantly use free software/products such as Linux, Python, SageMath, Octave, Wikipedia, etc.
I know that one can include software costs such as Matlab, Mathematica, Maple, Adobe stuff, Mac software, etc. But for free software/products I have not heard of anyone doing that. It feels wrong that if I use Matlab/Mathematica/Macs in my research, I can get public funding to pay MathWorks/wolfram/Apple thousands of dollars, but if I use Octave/SageMath/Linux they do not receive anything.
In other academic areas something similar can happen. I assume the same happens with "open" databases that operate with donations vs private databases that mostly operate as for-profit. Other examples could be Wikipedia, OEIS, LibreOffice, Gimp, etc.
I think that since a lot of research depends on that free software/product, they should receive funding (at least if you heavily use it). I know they receive funding elsewhere, but it is minimal compared to the money proprietary-software companies get (a lot from grants, by the way).
Do you know of cases where donations costs were included in grants? Do you think it is the ethical thing to do?