With JBoos, Tomcat and Websphere Liberty there are three application servers listed in the Volt MX Foundry Topology and Components page.
But I found no prerequisites for Websphere Liberty on the Application Servers Prerequisites page and no installation documentation on e.g. Installing Volt MX Foundry - Console-mode (for command-line-driven installations), too.
-- update --
I found the note "Important: VoltMX Foundry Installer supports Tomcat and JBoss. " on this page Volt MX Foundry Topology and Components . Please add this note on the top of the "Application Servers Prerequisites" till Websphere Liberty is part of the installer.