We included Plus in the free app package by mistake way back in January, making all free users effectively have access to all Plus features if they enabled the DLC in the apps' settings here on Steam.
We found the issue and rolled back the inclusion.
We're not rolling back any data, all meta data (normally Lite and Plus only) made by free users during this time will stay in each users' library and will still be usable for sorting, creating new nodes, links, etc, with the ability to create and update meta data with Lite and Plus.
Stay clear,
David