Original TheDAO reworked by a team of security experts to act as a core governance system of the project. The code is based on the Slock.it TheDAO and reworked to serve general governance purpose of the whole Callisto Network ecosystem as well as to define an automated onboarding process for new investors.
Here you can find the original DAO whitepaper (unavailable on Slock.it resources anymore): Whitepaper
The folder DAO2016 contains the original code of TheDAO1.0 rewritten with 0.8.10 solidity syntax by @Dexaran.