Regarding the image guidelines on CN:

There's a section in the Terms of Service that explains how to handle these matters (Posting from other sites, and copyright and privacy issues).
I rewrote the DSO Forum and Image Posting Guidelines in the hope to clear this issue.

In case you still have questions on this matter, you can either contact a moderator or an admin directly, or you can post your question in the Cloudy Nights feedback forum.

Hope this helps!

Olivier Biot
Cloudy Nights Moderator Team - DSO