1) Developers email address is a GMAIL account.... not even a professional company domain address.
2) website doesn't list where the servers are located, how many, or bandwidth.
3) purchase of VPN plan is NOT anonymous and can be tracked, because it goes through the app store; developer claims he does not keeps logs of activity and that MAY be so, but there is still a paper trail and history of the purchase attached to the account, stored by Apple for the rest of time.
So if the whole point of VPN is security and anonymity, there are probably better choices