No, I'm not saying that's a rule here, just answering your "Here's a philosophical question for you." with my ideas.
Edit: I took it to mean any competition entry.
The nub of the rules here are, as cited:
- From General Rules:
"[20] Any photograph a member presents on Ausphotography, whether by uploading to the site or displayed directly within the site using the IMG tags must be taken by and copyright owned by the member. The only exception..."
- From Comp Rules:
"9. The photographs entered must have been taken, and edited by the member. Use of someone else's photograph, elements, composites or textures will result in disqualification and may result in a permanent ban from Ausphotography."