JK2 has been put in maintainer mode and no further development will take place. The reason for shutting down JK2 development was the lack of developers interest. Other reason was lack of users interest in adopting JK2, caused by configuration complexity when compared to JK.
The latest official JK2 release is 2.0.4.
JK2 will have it's successor within core Apache2.1/2.2 distribution. We have developed new proxy_ajp that is an addition to the mod_proxy and uses Tomcat's AJP protocol stack. It is developped in httpd-2.1 and integrated in it. We have also developed a new proxy_balancer module for load balancing http and ajp protocol stacks.
JK will be fully supported for all other web servers. The next JK release is planned for the end of November. Lots of code from JK2 has been ported to JK

The Apache Jakarta Tomcat Connector - Documentation Index