Complex sentence: He has been active as an artist in the Swedish workers movement since his youth, including the very successful Tältprojektet, "The Tent Project", a musical theater performance on the history of the Swedish working, which toured the country the summer of 1977.
Split into simpler sentences: He has been active as an artist in the Swedish workers' movement since his youth. His activites include the successful Tältprojektet, "The Tent Project", a musical theater performance on the history of the Swedish working class that toured the country the summer of 1977.