I was wondering, if it is okay to use Zenphoto for commercial use or not. I've had a few requests from fellow artists to setup portfolio sites using Zenphoto, but I don't know if it is okay with the developer(s). I would of course give full credit and link to Zenphoto.

Of course, the GPL licence Zenphoto is released under explicitly allows that and artists portfolio sites are exactly what Zenphot is made for.

What we do not like is to post "hidden spam" to gain mor search engine ranking, so I removed the link in your post.