The front page says what Reason Commons is for

The home page and About now open with what Reason Commons changes for a group: talk a goal or a problem through and come away with a shared picture of what you are trying to achieve and what you will do about it. The method underneath is still explained in the Guide, and the main button now leads to the skill. Earlier framing that no longer describes the project has gone from the current pages, and a site check stops it coming back.

Two skills built for the retired Reason Commons app, ltp-project and ltp-visualize, are retired too; reason-commons is the skill to install.