I have several pictures of various stuff in my hard drive (mostly cities and mountain/nature view in the Philippines). I was thinking of uploading them in a photo gallery website where everyone can freely get pictures and use them. I would love to submit all my pictures to Public Domain, but then I realized one catch. What if somebody harvest all my pictures and launch his or her own competing website? So instead of full public domain, I was thinking of retaining some rights to myself. I visited Wikimedia commons and found that their photos are either public domain or GNU Free something (sorry, I'm weak in legalese). When I examined the document, it's really long with preamble and other legal stuff. My terms are very simple, everyone can use my pics for whatever purpose except for creating another stock photography, photo gallery or photocollection site. It can be stated in just one to three sentences. So do I have to make an elaborate legal notice like the GNU in Wikimedia or is it enough to express my terms in its simplest form with one to three sentences?