readme-ms.txt in s2Member – Excellent for All Kinds of Memberships, Content Restriction Paywalls & Member Access Subscriptions 120213, at readme-ms.txt
Yes. s2Member and s2Member Pro are both compatible with Multisite Networking. After you enable Multisite Networking, install the s2Member plugin. Then navigate to `s2Member -> Multisite (Config)` in the Dashboard on your Main Site. You can get started now, by turning on [Multisite Networking](http://codex.wordpress.org/Create_A_Network) inside your installation of WordPress®.