The Everything Source Code is available thanks to the courtesy of The Everything Development Company - http://everydevel.com (see the bottom of the page for a direct link). But do not let them confuse you! It does not mean that you will get the E2 Source Code directly and on a silver plate. There is only the engine itself available for download, although some additional nodeballs provide similiar functionality (well, a fairly large subset of it, at least) as Everything2 (namely combination of eMessage, EWiki, experience, ... - you must look around a little more for some of these, though; /msg me if you will have any troubles).
The Everything Engine is a lot more versatile and universal than you might think - people use it even to run their homepages as they can easily use its noding mechanism as a notebook, guestbook, calendar, scheduler, weblog, discussion group, image gallery and so on. However, in order to be able to run it, you should have some general perl experience - it is not still free of all bugs and you can meet some problems along the way, especially if you are trying to set up something complex. However, if you will get through, you can take merit of genial and supermodular design of the whole engine. The only little limiting factor is low speed, which is a tradeoff for the highly hiearchical and abstract design; the developers are working hard on enhancing the speed, though.
For your information, Everything2 runs on a huge meatball of patches built around of version 0.8 of the engine.. at the time when this writeup was written, the actual version of the engine was 1.0-pre2.
The Everything Engine is distributed under the artistic licence, that means you can use it freely, even for commercial purposes. | 
