Which versions of Sony Vegas include the Cineform Codec?

Vegas 6, 7 & 8, include a old 2.x version of the codec. It is limited in it quality controls it can't decode newer images generated with 3.x codecs.

It is limited in it quality controls it can't decode newer images generated with 3.x codecs.

What are examples of 3.x codecs? Are you talking about images generated by cameras? or something you render in a timeline?

It just a version number, CineForm has continued to enhance the codec such that the old codec will not decode new files. The new codecs have improved quality and speed and support many new features like Active Metadata.