That is likely because a lot of DRM relies on security by obscurity at least somewhat, and therefore being open is sort of defeating the point a bit.
However, there are at least 2 relatively open DRM systems that have specs publically on how to implement at least part of it.
They might be considered a good place to start if you are looking for how to implement DRM.
You are not likely to see a lot of public discussion on the code obfuscation parts though. But in terms of the infrastructure and how to define rights, they might be provide good templates.