I am taking from this post that the Foundation is able to receive donations.
However the way to do that is not properly set up as far as I am aware of and I would not be surprised if there weren’t any donations made ever.
The “Donate” button on the top menu here leads to the membership site of the Foundation which consequently means there is a certain level of bureaucracy involved (becoming a member) and the minimum amount of a donation was USD 200. Also existing members could not donate on top of their membership (beyond getting a second one).
I believe this does not suit the needs of someone who wants to give back something spontaneously (because he/she had a good experience here in the forum i.e.) because it is too complicated and the amount too high.
I believe there is a very easy way to solve this blockage by setting up a paypal.me link for the Foundations PayPal account and link it to the “Donate” button.
That way any amount could be donated with a very limited amount of actions required. And I believe this should be possible.