Which Distributions Can be Freely Copied and Distributed?

Official commercial distributions, may contain installation utilities or commercial software that cannot be freely copied or distributed.  Often the non-free software will be placed on separate CD(s) or in a separate folder on the CD(s) (with a folder name such as "non-free"), so that it's easy to recognize which can be freely copied and distributed and which can't be.  The distribution may also come with documentation explaining where the non-free software is found on the CD(s).

The official commercial vendors offer a version of their distribution that can be downloaded for free; however, there may potentially still be restrictions on the copying or redistributing of the software.

Unofficial, non-commercial distributions can be freely copied and distributed.  The reason they can be sold for such a small price is that there are no licenses for which the reselling distributor has to pay fees to or receive permission from the official distributors.  This same lack of restrictive licenses allows the end users to freely copy and distribute them in turn, and to sell them if they wish to.