According to a Belgian architect bureau I have been in touch with (and the Atomium itself), FoP in Belgium is valid only for non-commercial purposes, because of the Berne 3-Step-Test. See attachment.

I find this explanation very unconvincing, because the so-called 3-Step-Test is valid in all EU Member States and thus would mean that FoP for commercial purposes is questionable everywhere in the EU.Furthermore, I would argue that the "normal exploitation of a work" in the case of architecture isn't printing it on a T-shirt and selling it.