who needs GD songs?
depending how the movie plays out, if the film chronicles Garcia's pre-GD dayz, the film can still survive minus the GD hits.
Just have actor-Jerry pick away on traditional bluegrass ditties with the Sleepy Hollow Hog Stompers and then show the transition into the Warlocks era 60s rock/psych/blues cover tunes. And if they go into the Acid Tests, I doubt the film will run into trouble with experimental freak-out jams.
Take a look at Gus Van Sant's "Last Days" that chronicled the dreary days leading to Kurt Cobain's suicide. As I recall, no Nirvana tunes were used, and the film still succeeded imo. There's a far-out dramatically intense scene where actor-Kurt strums on the guitar and sings his pain away...
Or that Jimi Hendrix biopic, "Hendrix" that just showcased actor-Jimi performing the cover songs (Hey Joe, Wild Thing, etc...). Jerry's movie can showcase his early days and conclude by fast forwarding to the 90s as the GD encore with