There is no national bookmaker licence in South Africa. Nine provincial boards issue them, and an operator holds one or more provincial licences. "Licensed in South Africa" on its own is not a meaningful claim — the province and licence number are what matter.
Step 1 — find the licence number
Licensed operators display their licence number in the site footer, usually alongside the issuing board. If you cannot find one, that is itself the answer.
Step 2 — identify the board
The footer should name the issuing authority. The nine provincial boards are Western Cape, Gauteng, KwaZulu-Natal, Eastern Cape, Free State, Limpopo, Mpumalanga, Northern Cape and North West.
Step 3 — check the register
Each board publishes a register of licensees. Confirm that the operating company named on the licence matches the company named in the operator's terms and conditions. Brands frequently trade under a different name from the licensed entity, so check the company, not just the brand.
What is and is not licensed
Sports betting and horse racing are licensed for online play in South Africa. Online casino games are not. An operator offering online casino games to South African customers is operating outside the licensed framework, whatever else it holds.