I just checked the license for the IP you mentioned and it is premium. Sometimes there is a minor delay of around 2-5 minutes from payment processor where it makes some fraud checks and they send us the IPN after that the payment is marked as successful.
Regarding the double charge I checked with our payment processor and we have received the payment only once. If you are charged twice please send us the transaction id via Ticket and we will check it asap :
https://softaculous.deskuss.com/