We have been impatiently waiting for the maturation of java-based CMS components and engines that could be mixed and matched in an appserver to meet specific business needs. It appears now that this approach may be seeing some daylight. Witness ex-NASA developers at Oak Grove Systems, who have built a J2EE-based workflow engine. Put this together with a versioning system and deployment engine, and you have three-fourths of a CMS back end. Best of all, you didn't "build it yourself," you merely assembled it yourself -- and that might be better than buying the whole works from a single software provider, with assembly still required anyway...
Check out Oak Grove's "Reactor 5" Workflow Engine