Marin moved into a building, formerly owned by the Grateful Dead, which included offices, warehouse space, and a recording studio. After the sale of the building, the surviving members of the Dead carried on using the recording studio for a while, but under lease. More info here: https://www.pinkbike.com/news/inside-marin-cycles-reawakening-historic-brand-2014.html.
To my knowledge, the Dead never owned Marin bikes although there were other connections between the Dead and the early mountain bike scene.