Here you can find the documentation for recent versions of OpenMDAO.
latest    
Released on June 28, 20223.17.0    [Release Notes]
Released on March 21, 20223.16.0    [Release Notes]
Released on January 6, 20223.15.0    [Release Notes]
Released on November 24, 20213.14.0    [Release Notes]
Released on November 18, 20213.13.1    [Release Notes]
Released on October 14, 20213.13.0    [Release Notes]
Released on October 6, 20213.12.0    [Release Notes]
Released on September 15, 20213.11.0    [Release Notes]
Released on August 3, 20213.10.0    [Release Notes]
Released on July 14, 20213.9.2    [Release Notes]
Released on May 17, 2021latest_20220418    [Release Notes]
Released on April 18, 2022latest_20220418b    [Release Notes]
Released on April 18, 2022latest_20220415    [Release Notes]
Released on April 14, 2022