Ported numbers DO have an additional $9.95 annual fee
When you port in a number to MagicJack, you pay $19.95 at the time you do so. Also, you have to pay an additional $9.95 (on top of the $29.95 annual fee to use your MJ) to renew the number each year.
MJ will start bugging you about 30 days before the renewal is due that you have to renew the number. If you ported in, you would then lose the number forever if you don't renew, or port the number out to another provider.