"InfoPath isn't part of Office"
"Then you find out its not part of the office suite."
To be fair, this is somewhat true. At best, it's confusing.
With Office 2003, InfoPath wasn't part of the suite you could buy retail or on open license. However, if you bought Office Pro on an enterprise agreement, you did have rights to InfoPath for every desktop.
Unfortunately, in the volume license media, there were two DVD's: one labeled "Office Professional" and another labeled "InfoPath." You had to understand the licensing to understand that you owned InfoPath.
This is much better in Office 2007, where InfoPath is in Office Professional Plus, Enterprise, and Ultimate.