Make sure you check which BOSU you have. The professional ones hold more weight than the consumer grade ones. I have the pink breast cancer ones and they’re for less than 300 pounds.
Most equipment holds a lot more weight than it’s rated for, but I’d be wary with a client who is above the weight limit. If it breaks on the client, it’s going to be on you, not on BOSU, since you’re using it outside their recommended allowance.
Jason, above, asked a valid question. Why jump on a BOSU? Make sure you can articulate your “why” to your client if you’re doing this activity. I’m not saying don’t do it. I have clients who jump and land on BOSU, but not every client. Gotta have a reason.