Twitter Open-sources FlockDB
But the Ruby code appears to be a mess and unusable.
"We have not yet pulled over the main file so it wont actually start a thrift service. So it can't yet be used," according to the "How to Actually Use" section of the README.
Twitter said that they're in the process of packaging the software to be used outside of Twitter, but for now "it is very rough as code is being pushed around."