Thelonious (not in use any longer) was the Eris Industries fork of go-ethereum, forked in September 2014 (~POC6). We have kept somewhat up-to-date with that repository, and will continue to do so, but its rate of change is currently too high to integrate everything. Thelonious is not intended to compete with Ethereum directly, the way other forks might. It is not intended to be a single blockchain, either. Rather, it is a window into experimenting with and utilizing the ethereum technology.
Thelonious' primary contribution is the monkdoug package, which facilitates the deployment of customized genesis blocks and blockchain protocols that can be scripted using the same tools used for contract development (namely, EPM).
Thelonious intend to be much more flexible than ethereum could be, by adding and experimenting with different opcodes, virtual machine designs, and protocol rules. Perhaps something useful will emerge from these experiments that will inform and enhance the Ethereum project itself. Perhaps you will simply have fun. Either way, we are content.