Nuspec tag use clarification request for 3rd party projects producing binary from original software

This is a follow up on [Google Groups thread](https://groups.google.com/forum/#!topic/chocolatey/7G9zHT0zYEg) on ambiguity of binary producing projects vs software project and alike and how to fit all this into Nuspec tags with appropriate aliases.
For example, should _projectUrl_ point to original software source project or an unofficial 3-rd party binary producing project URL that we are packaging with Chocolatey?