Yes, you are right. Once you stop paying for the subscription, you lose access to the cloud sync but the basic program will still work on your computer.
For subscription plan you would need to pay annually - This will allow you to keep all devices (any number of computers, iPhone, iPad, Android devices) in sync. And, if you choose One-time-payment option, then it is just for Windows version of Notezilla and you will have access to your program on your Windows desktop only.
For more details on the pricing, please visit : www.conceptworld.com/Notezilla/Buynow