YubiKey Validation Server was first developed by Yubico and Yubico made it an open source project starting from June, 2008. Anyone that likes to participate the development work please contact send your bio, availability, modules you are interested to work on to Tech@Yubico.com. Yubico will continue coordinate the community efforts and make enhancements in new releases regularly.

Check out project documentation here: http://forum.yubico.com/yubico-val-server

If you are a user that wants to deploy a stable release, you can get the stable releases by checking out from the release tags. Eg.

svn checkout http://yubikey-server-j.googlecode.com/svn/tags/release-1.1 yubikey-server-j-read-only

As a developer, you can get the tip of the trunk which is the most current development:

svn checkout http://yubikey-server-j.googlecode.com/svn/trunk/ yubikey-server-j-read-only