In synopsis, the practice is essentially thus:
* Prefer "free" media, the freer the better. Keep future CZ re-users in mind and try to craft articles as units that can be re-used as wholes.
* Some apparently "free" media is not (e.g., from Wikipedia). The photo must be released under a real name.
* You may but should try to avoid using copyrighted images by permission in CZ. Do this only after unavailability or clear inadequacy of free media is evident. In this case, also ask for the permission to extend to re-users of CZ if you feel it is appropriate to do so with the particular copyright holder; otherwise, such images will very probably not be usable by Citizendium re-users.
* Totally avoid "fair use" media—at this point. Seek licensed release or permission instead. A policy proposal on fair use media is currently on the table so this is subject to change hopefully soon.
* Document everything carefully—all license releases, all permissions, all image sources. Use the guide and the fill-in box and the drop-down list at
http://en.citizendium.org/wiki/Special:Upload and everything should be fine.
* Problematic images are subject to deletion.
You can also go to
http://en.citizendium.org/wiki/Help:Images#Copyrights although it needs some minor updating at this point, and could frankly stand a good re-write for clarity and brevity.
Feel free to ask me any questions on my talk and don't overly worry about making a mistake or two. I and others monitor images uploaded very frequently, so you'll definitely be let you know if something you upload needs fixing and how to fix it.