Yup, that was a couple plugins API ago, and the current one is undocumented, hence the stall on that front

. (I worked on the tooling bits, but I don't really do C++, so I can't really help much after that ^^. @geek1011 should be able to tell you more).
Take a look at the age of the stuff you're cloning, you probably don't need 99.99% of it. In fact, I'll save you some trouble: the only thing you might want to take a look at are the kernels. Other than that, possibly the lightly tweaked Qt 5.2 modules (but it won't really tell you much more than: it's Qt 5.2, so, eh), and that's it?