Fixing packaging terminology confusion

Edit: the discussion is still going on, so I've probably blogged that a little bit early (I was excited about it ;)). Stay tuned for the final output.

Brad Allen launched a thread in Distutils-SIG about packaging terminology confusion. In particular the usage of the word "package" in our community. Part of the confusion is because of the meaning of this word in Python (that is, a directory containing one of several Python modules, with a special one named and in some systems like Debian (there, a package is a distribution file for a library or an application).

This confusion was present in PEP 345 (which was started years ago, so that explains it) - and is present in Distutils documentation and also in PyPI (That is: Python Package Index).

I really like Tres Seaver's definitions, because they match prefectly the reality:
- package means a Python package, (directory intended to be on sys.path, with an We *never* mean a distributable or installable archive, except when "impedance matching" with folks who think in terms of operating system distributions. - distribution is such a distributable / installable archive: either in source form (an 'sdist'), or one of the binary forms (egg., etc.). Any distribution may contain multiple packages (or even no packages, in the case of standalone scripts). - project is the process / community which produces releases of a given set of software, identified by a name unique within PyPI's namespace. PyPI manages metadata about projects (names, owners) and their releases. Every real project has at least one release. - release is a set of one or more distributions of a project, each sharing the same version. Some PyPI metadata is specific to a release, rather than a project. Every release has at least one distribution.

And I really like Martin's proposal in the thread (in Catalog-SIG since it was cross-posted): "PyPI would then be the Python Project Index."

I'll fix Distutils documentation on my side accordingly, as well as the guide we are building. Let's promote these definitions :)