I have posted a draft REP 114: rospkg standalone library. It is
intended as a rewrite of the roslib Python library, this time with a
publicly supported API.  It is also standalone, i.e. it can be
installed separately from ROS.  The intent for this library is to
support develop of ROS tools that are decoupled from a particular ROS
distribution release as well as become the basis for future ROS tool
bootstrapping.

http://www.ros.org/reps/rep-0114.html

At its heart it can be thought of as a Python rospack/rosstack, though
it goes a little beyond that.   The first targeted use of the rospkg
library is a rewrite of the rosdep library to also be standalone.

The REP notes current open questions/issues for discussion.

I have also written documentation here:

http://www.ros.org/doc/api/rospkg/html/sphinx/html/

It includes the start of a developer's guide for those that wish to
also develop/maintain this library.  As this library may become the
bootstrap library for ROS in the future, I encourage those that are
interested to get involved.

cheers,
Ken