Thanks. This discussion is very helpful but sometimes a lot of confusion.
Summarizing one should add in the buildout config file to the section
index = https://pypi.python.org/simple
This I have tested for Plone 4.0.1 and 4.3.14
In both cases it works. There are only some warnings which are not so clear for me:
For 4.3.14 the installation came up with following warning:
/usr/local/Plone4/buildout-cache/eggs/setuptools-27.3.0-py2.7.egg/pkg_resources/__init__.py:188: RuntimeWarning: You have iterated over the result of pkg_resources.parse_version. This is a legacy behavior which is inconsistent with the new version class introduced in setuptools 8.0. In most cases, conversion to a tuple is unnecessary. For comparison of versions, sort the Version instances directly. If you have another use case requiring the tuple, please file a bug with the setuptools project describing that need.
Maybe someone have a hint for me.
Details about the addon-Products I will not discuss in this theme group.