Oh man, hows that for a bad joke?
Due to the shortage of residences, I'm afraid your housing accomodations have been reallocated.
The SDK stands for "Software Development Kit". This is a general terms used in programming circles. It generally implies a set of interface bindings, and possibly some library code to help with common tasks, and is used in developing software for a certain platform (such as an OS, or a game). As there is only one such package around these forums, or for Outpost 2 development (that anyone here knows of), it tends to be known as "the" SDK. I suppose some of the other projects like IUnit, or the badly named ForcedExports project are somewhat SDK like, but these are generally used in addition to the normal SDK or as addons rather than being alternates, so they've never quite achieved the same status.
The SVN would be a good source of sample code. There is an updated SDK in there, and some levels people have been working on (although, not as much level code in there as I'd like). I can't really speak for the polish of everything in there, particularly level code that other people contributed. Keep in mind that most things in there are development versions, not release snapshots. (The tag folders tend to be release snapshots, but most projects that have tags are a little more stable and probably more worth looking at the development trunk).
Edit: The SVN is readonly to the general internet. If you need a write account, either to add a new project, or help/update an existing one, you'll need to PM me about it.