HTC does not have a github. They never have and likely never will. The only source that manufacturers are required to give is kernel source, since that is licensed under the GPL (which requires all changes to source to be published). Most of Android is licensed under the more lenient Apache license, which means manufacturers may give out source, but are not required to (read: don't). HTC is not under any obligation to release any source outside kernel and doing so would give their competitors an advantage and facilitate projects like these, which HTC doesn't want as they get nothing for it.