It is simply not possible for us to add a "donation" cost to our projects. That will not get past accounting.
A license, on the other hand, we would have no issues purchasing that.
We purchase (expensive) licenses to proprietary software all the time. We could and would do the same for the open source software, we use, but without being able to purchase a license, there really isn't any practical way of doing that.
Free for everyone, except for enterprise production environments, would work for us. As long as we get a license key and an invoice.