There are two options for obtaining a copy of KOS for your use.

Option #1 is to download a release archive. These are snapshots made of the working tree once in a while and have an associated version number in the same style as Linux kernel releases (e.g. 1.2.1). An even middle digit implies a "stable" version, meaning the API will not change significantly if you upgrade to a new minor release (1.2.2, 1.2.3, etc). An odd middle digit implies a "development" version, meaning you will get the absolute latest goodies here, but you may or may not have any real stability. You may find yourself rewriting chunks of your code to a new API or other drastic changes.

Note that there hasn't been a "release" of KOS for several years now. The release versions are quite old and don't really reflect the current state of KOS well at all. It is thus highly recommended to look at the source control for a more up-to-date solution. The SVN versions of KOS are generally pretty stable and don't really tend to throw away the old APIs as the paragraph up above may suggest.

Release archives can be obtained here.

Option #2 is to follow the source control. This is bleeding edge stuff, but it's generally recommended anyway because KOS itself is pretty stable. If you want to follow the devel version (e.g., 1.3.x) then you need to be on this version. If you make local modifications to your tree then you probably also want to be on here so you can merge new updates. Note that it's also possible to follow a branch, for example the 1.2.x branch. This lets you track the "stable" versions in a simpler way.

KOS is now developed (as of early October 2003) using Subversion. For more info on getting setup with that, go here.