Thanks OM! I guess I will have to get a third professional opinion on this. I assume it is usual income too. It would be too good to be true otherwise.
Nevertheless, it could be interesting to you too that they changed the name from "Patent Box" to "Innovation Box". One Tax advisor told me that any income generated in the form of Royalties by "intangible goods" such as Software, Patents, Industrial Designs, 3D Models or _Images_ (as they are a intangible product of a creative process) can be placed in the "Innovation Box" and as such are taxed only with 5%.
I am not yet in the Netherlands and the answer to this question will be crucial for my decision to move there or not.