The Source Code for the entire Oracle Coherence Incubator is hosted by github.com.
It is located here: https://github.com/coherence-community/coherence-incubator
Alternatively if you're not using or want to avoid setting up git can download a zip containing of the latest development branch from here:
The branching model adopted for development and releases is as outlined by Vincent Driessen in A successful Git branching model
Active development is carried out in the branch: develop-12. Nightly builds, snapshots and continuous integration typically occurs on this branch. Snapshot releases from this branch are made available on http://maven.java.net in the snapshot repository.
Official Releases are made from the branch: release-12 (once integrated from the development branch). Each official release is tagged. Official releases are published to http://maven.java.net and later (usually with in 4 hours) to Maven Central.