The OASIS Service Component Architecture (SCA) standard appears to be used by several established ESB vendors like Oracle, IBM and TIBCO, however the newer ESBs like WS02 and Fuse ESB don't use it. The spec and any references to it seem to be 4-5 years old, and some of the spec links on the OASIS site are broken, so I worry that the standard is perhaps dying.
Any thoughts on this?
The specs are complete and waiting on two implementations to claim conformance before going to vote for finalization. This is taking time since claiming conformance is a lot of work. The more recent specs (published about a year ago) should be available publicly. Note, it is highly unlikely things will change during this waiting period since the technical committee work has long finished.
Fabric3 (www.fabric3.org) is conformant with the Assembly spec. The new JBoss integration platform, Switchyard, is moving to SCA but after reviewing the documentation, it only implements partial support for the standard. Apache Tuscany (http://tuscany.apache.org/) and Tentino (http://trentino.sourceforge.net/) also support SCA, so that makes 4 open source SCA implementations I am aware of. I believe Tuscany has also claimed conformance to Assembly and possibly other specs but I can't speak for them.