Early customers, who've deployed the Mattermost platform, contacted us, and are seeking a commercial "enterprise communication" solution, have access to pre-released builds of the enterprise version that includes LDAP SSO.
We're working with them to validate the feature set and roadmap for the enterprise release, which should be availabile in Q1 2016. SAML, Kerberos and custom SSO are among the features requested.
We plan to release new builds monthly, and specific features will depend on feedback from early customers of the commercial version.