According to Birchwood Casey's MSDS, Gun Scrubber is made with trichloroethylene (TCE). You can scroll down to the Gun Scrubber listing and view it for yourself here.
http://www.birchwoodcasey.com/sport/msds.asp
Many hazard warnings associated with TCE, not many places allow the use of this chemical anymore.
PD-680, Military Dry Cleaning solvent suffered the same fate as the health hazards became known. It had CFC's and is on the banned list for depleting the ozone layer.
Many people use Chem Dip, which is a solvent used primarily for automotive use. It can be found in auto parts supply stores in 5 gal quantities. But using this material can damage wood and plastic components, so these must be removed prior to usage or they will be damaged by this solvent.
Using Kerosene is another alternative. Kerosene is one of the main active ingredients in Hoppe's Cleaning solvent. You can scroll down here to view Hoppe's MSDS.
http://www.copquest.com/knowledgebase/index.htm Just be sure to relubricate all the metal parts after using Kerosene for gun cleaning/carbon removal.
If you want a good homebrew recipe here's one for Ed's Red.
http://www.building-tux.com/dsmjd/tech/eds_red.htm
Hope this helps.
R,
Bullseye