On Amazon AWS Marketplace you can look for "OpenVPN Access Server". You'll see a number of results. Most of these results have at the end (xx connected devices) in the title. This indicates that when you launch such an image from the AWS Marketplace, that it will be automatically licensed for the specified amount of connections. This gets billed through Amazon directly. The costs are separated into software licensing costs and AWS instance costs. These are billed hourly. If you launch an OpenVPN Access Server (xx connected devices) type instance on Amazon AWS you will incur charges for the use of the software and charges for the use of the instance you've launched while the instance is actively running. If you stop the instance, you will stop incurring additional costs for the software licensing and running the instance. Some charges may still apply for simply having the instance, like storage costs, but those will be minimal. It is therefore possible to use such a system on demand, or in other words to have an instance on cold standby ready to be launched when needed.
The OpenVPN Access Server for 5 connected devices comes with a temporary free trial. That means that when you launch it, for the first 7 days, there will not be a software licensing cost billed to you. This allows you to test it out with 5 connections. You will still pay for the infrastructure costs of running an EC2 instance on Amazon AWS, although you might be able to make use of the free trial options that Amazon AWS itself offers as well. If this instance is still running after 7 days, then the software license billing will start. Day 8 will then be day 1 in terms of software license billing.
There is also an offering on the AWS Marketplace that has no connected devices specified, and is of a typo called BYOL, which stands for Bring Your Own License. This Marketplace image when launched will only allow 2 connections. That is what you get when an Access Server is unlicensed. If you want more than 2 connections, you can purchase an activation key from our website to unlock more connections. This activation key gets billed by OpenVPN Inc. directly and doesn't get billed through Amazon AWS. The infrastructure costs for running an EC2 instance on Amazon AWS still applies and gets billed by Amazon itself.