[Clipart] [Open Clip Art Library] license problem

[noreply at openclipart.org]

Hello,

today I had a look through several images and designers at openclipart.org. I followed a link in one of the designers profile to his website. The terms of use there said his images are for non-commercial use only. 

If I understand the Public Domain Dedication at creativecomments.org right, this stands in conflict to the Public Domain License. 
Per mail I asked the user about his images at openclipart.org. I quote from his answer: "all my images on openclipart.org are ONLY FOR NON-COMMERCIAL use."

Can he release images in the public domain and still say it is for non-commercial use only? I thought if he release an image to the public domain he don't has that right anymore and I can use it for any purpuse what includes commercial use. 

An information on this would be deeply appreciated. 

Thank you for your time

regards

Jarod