Tame Iti has been teaching fellow inmates te reo Maori in Waikeria prison.
Iti, and Te Rangikaiwhiria Kemara, were jailed in May for their involvement in military style camps in Te Urewera National Park, in 2007.
Both men are appealing against their convictions and sentences.
Iti's son, Wairere Iti, says his father has been actively participating in the prison community and is teaching te reo Maori as well as mentoring younger inmates.
Wairere Iti says his father has also been painting in prison and one of his artworks, titled: Te Whai A Te Motu, will be auctioned to help with his appeal costs.
