Which version of OpenVPN to use
To make that decision it helps to know the general specifications of the available programs. Generally speaking there are two main branches: the commercial programs, and the open source programs. First we'll describe our commercial offering, followed by a description of the open source program.
The OpenVPN Access Server product is a great way to easily set up a secure and easy to manage OpenVPN server and has a web based system to manage configuration, certificates, users, groups, and access control, and comes with professional support from the OpenVPN Inc. company itself. It is free to install and use for a maximum of 2 simultaneous VPN connections, so you can trial it without having to pay first. If you need more connections, you can purchase a license key from our website and activate it on your server, or use a licensed tiered instance on Amazon AWS which is billed directly through Amazon. The pricing structure is very clear and not the type of "request a quote" you see with many other programs, and can be found here on the pricing overview page. The Access Server must be installed on a Linux operating system, but this can be a virtual machine making it possible to install this on almost any host platform. While the Access Server program must be installed on a Linux operating system, the clients that can connect to it can be Windows machines, or Macintosh, Android, iOS, or almost any Linux system. With Access Server there's a very clear separation of purpose; the OpenVPN Access Server runs as a server accepting incoming VPN connections. And OpenVPN Connect Client, or a compatible OpenVPN open source client, can start a connection to this server.
To see which platforms the Access Server are usually deployed on (by no means a complete list) see the installation options page.
The OpenVPN open source project focuses on the core program and is available for many platforms. It can run as client or server on Windows, Macintosh, and Linux. Configuration is done with text files with directives that tell the program what to do, and you have to manage certificates yourself. There is less of a distinction between server and client here; this just depends on what configuration directives you feed the program. If you tell it to be a server and accept incoming connections, it will do that. If you tell it to start a connection as a client connecting to an existing server elsewhere, then you can give it the configuration directives to do that, and it will do that. You'll note that we didn't mention iOS and Android in the list, but they are supported. On iOS and Android the same client apps available there that let you connect to an OpenVPN Access Server also work for connecting to an open source OpenVPN server. Likewise the open source OpenVPN program used as a client can make a connection to an OpenVPN Access Server as well, since they are compatible because they use the same standardized OpenVPN protocol.
There are a great many services and programs built on both our commercial OpenVPN Access Server product and the open source OpenVPN project. So many in fact that it is next to impossible to list them all. This documentation here however focuses on the commercial OpenVPN Access Server program and client devices and programs compatible with it.