I think Warners released the film and the soundtrack, but the film was produced by Regency (formerly New Regency—odd?) and Canal+. I know some Regency titles are now part of the 20th Century Studios library, so yeah, maybe I'm just trying to keep this Danny Elfman expansion dream alive.
Sommersby was/is produced by Arnon Milchan's Regency company. Disney doesn't own the movie or that catalog, but they continue to distribute their theatrical catalog at the moment as Fox had previously (and Warner had at the time of Sommersby's release).