Users are not able to edit the entries, but have to go via the OP.
This isn't the proper format for such a thing. There are wikis that are better suited for this sort of material.
I agree, a wiki is a much better way of doing what you have started.
Here is a list of GPL licensed, PHP based wiki engines,
http://www.clickonf5.org/7599/10-free-opensource-wiki-software-engine/, check my sig for free cpanel hosting (that will handle PHP)