I'm a regular user of DBM, but lately I'm seeing more and more videos and UI compliations of top guilds where Vision Boss Mods (VBM) is mentioned. Search with Google, on Curse and Wowinterface turned up negative, the only information I could get that it appears to be some sort of "invite-only" addon.
Does anyone know more? Why it is so restricted, who it was written for in the first place etc?