After a two year affair, you have to wonder how he "donated" his sperm.
The article is pretty vague on the point, but I think you're right - this was nothing like 'sperm donation' as it is normally understood. It sounds more like the agreement (if it existed at all) was a ploy on her part to continue the affair - he acquiesced, and now has to face the consequences. The guy went back for a freebie and got stuck; no sympathy from me...