Yes, it is paid by all workers, including the self-employed. It seems there has been some costing done for self-employed workers, and it looks like the net cost is $420 per year for a self-employed worker.
Now, there's no option as to whether or not you will contribute; we consider it as part of supporting children of families across the province.
In terms of how long you need to contribute, as soon as you indicate you're self-employed, then you're eligible to contribute to the program.