Important things first: Many thanks Nikolaus for sorting this and for the fine solution you came up with.

On Neo900 UG side consultations with tax adviser (yesterday) resulted in him forwarding me to a lawyer, to develop the fineprint for donation page stating the details of how we will handle and what we will do with your donation. This probably will take several more days (need to find a lawyer willing to do this for a reasonable wages, and then actually develop a fineprint text that doesn't create similar trouble like we seen with the first one). Until this got completed, the [donate] button on Neo900.org will simply jump to a page providing not much more than the bare account details and an instruction what to put into the subject of any money order getting transferred to the UG account.
The spirit, idea and concept behind the donation remains the same, so for our donors nothing relevant will change, but we can't do it with that fineprint we had so far, that's been our big mistake we made. Again sorry for that.
Please stay tuned, I'm working on it to improve the user experience and the legal situation of the whole project.
Meanwhile I suggest and ask you all to simply agree on GDC forwarding your refund to the Neo900 UG account and to add your email-address into the subject of such transfer. Legally this turns your donation from whatever it's right now in the notion of german Tax Office into a true clean donation to Neo900 UG, something that it meant to be from beginning. By agreeing to this you also agree to GDC forwarding the data of your order (amount, date of transfer, special requests, etc) to Neo900 UG so we can handle your donation correctly. Again sorry for the noise and possible feelings of discomfort and uncertainty we created by this mistake we made, I hope we're now finally close to sorting it for good.

cheers
jOERG