The short answer is that you cannot.

The longer answer is that I either do custom developments out of a desire to help or because I get paid to do it (preferably both, of course).

By involving donations, it will feel like paid work, but I will probably get much less than my normal rates, leaving me unsatisfied.
It will also make the donator expect more in terms of support and feature requests, which is something I cannot guarantee on this site, simply because it is not putting food on my table - and since I am in Denmark, where prices are high, donations will have to be rather considerably higher than most people are willing to donate, before I feel that I get paid what I deserve.

By not accepting donations, I write code because I want to and when I want to and I give as much support as I can, without it being an obligation due to me accepting donations.

If you like what I do and want to hire my company for a custom development job, you should not look for donate possibilities here, but instead contact Cusix Software through the Cusix website

Some modules developed for clients are not suitable for release. Some are suitable only with some changes - usually due to client-specific hacks - but whenever possible, custom developed modules are made available to the XOOPS community as a whole.

Cusix Software is a small XOOPS consulting company, based in Denmark.

Cusix works for enhancing the quality of modules available for XOOPS. To achieve this, Cusix sponsors http://xoops.web-udvikling.dk for releasing open source versions of modules and themes developed for Cusix' clients.