I'm not an expert on any of the available FPV equipment. So I don't know what frequencies they use. You can find a nice Amateur Band Chart produced by the ARRL (Amateur Radio Relay League) at http://www.arrl.org/files/file/Hambands_color.pdf

If any manufacturer is using ham frequencies they should inform the purchaser that an amateur radio operators license is required to be legal.

In the 70's and 80's I competed in AMA pattern contests and I used 6 Meter Ham Radio R/C equipment. That required a Technician, General, Advanced or Extra Class license. Any ham operation above 50 MHz still requires one of those licenses.

Ham operators are very protective of their operating bands (because of government and commerical interest trying to taking them away) and will track down and report any illegal use.

Also be aware that Amateur Radio Operators cannot use the ham bands and equipment for any commercial purpose. For instance I could not fly my 6 Meter R/C airplane for money. Not that anyone ever offered.

Hope this helps.