Wart,
You have to complete a Radio communication application form for a "Aviation station license". It's not available electronically, but you can call ICASA in your area and request a fax copy. I have a very bad fax copy - will see if I can get a better quality and put it on the SAGPA website.
The application and the initial fees must be processed at an ICASA office, but the renewal fee can be paid at any post office or electronically using the license number as a reference.
I spoke to Mr. Putter at ICASA and he said:
Any electronic equipment capable of transmitting and receiving radio signals in the prescribed frequency ranges has to have a license. In the case of portable radio equipment used on aircraft an aviation station license is definitely required.
So there you have it; skybound is correct, and I suspect that ICASA will have an unexpected budgetary windfall for FY2006/2007 as I would wager that there are a number of hand-helds that are not licensed.
This is a license for the radio and must be renewed anually - not to be confused with the restrited radio certificate that you have to obtain as part of you completing your pilot licence.