That's not completely true, if you get an addon like Kryoflux for the pc/mac, you can write ADF images on a pc.
Well, in the future that is. The maker of the Kryoflux is working hard on it atm. With enough donations, he can take days off to work full-time on it.
As the topic submitter states, he/she runs a computer museum. In that case he/she should really look closely at the development of the kryoflux, because software development of the catweasel is stalled AFAIK. Meanwhile, I personally use AmigaExplorer for all my Amiga backup/restore needs. But then again I do have workbench.