Hold on a minute... buying Linux CDs and giving them away doesn't make you a distributor, does it?
Technically speaking, it does. You are distributing copies of copyrighted material and need to be in compliance with the licensing terms and conditions set by the copyright holders. To be honest, lawyers (at least Free Software ones) are not likely to come after anyone for failing to include source-code information when they give a copy of a Linux CD to someone else, but the General Public License
does require it*.
Other licenses also apply to the software in the distribution and must be honored; but to my knowledge all of the proprietary software included with Vector permits free redistribution, and the non-GPL free software licenses (BSD, MIT, MPL, etc) are less restrictive than the GPL in their distribution requirements.
* I suppose it is also necessary for GPL compliance that the distributor provide a patent grant to the recipient for usage of any patented methods owned with respect to the software being given away.