You can use your VPN offer on as many devices as you want. The limitation will be the simultaneous use that will depend on the type of offer you have chosen. The Bronze, Silver, Gold allows respectively 7, 12 or 20 simultaneous connections. For instance, if you have subscribed to a Bronze offer and you have already 7 of your devices connected, attempt to connect the eighth device won’t work until one of the 7 disconnects
Europamente VPN use the Open Source OpenVPN Connect client application that is available to download on PC, MAC, Android, Android-TV, iPhone, iPad. On MAC, there is also Tunnelblick Open Source application that can be used. On Linux it is natively supported via the network-manager package. DD-WRT also embeds the OpenVPN client support via the router web interface
The installation Guide for each system is available here