if you plan to do that, I suggest take a look at odinteh cause it was the direct fork of odinms before it died and before all the source went to shit, it is v75 but most of the development tools are available for that version
https://github.com/DannerrQ/OdinTeh
for the client you can find it around other developments. it depends on what you want to do with the source, either rewrite to use netty, removal of xml reading or use binary reading (in terms of speed) or mcdb ? maybe if you plan to really work on it you can always open source the project so people who are interested can contribute.
remember the best is to write your own code, since you will how it works and it wont cause any issues in the future :) given the seriousness you put in.