The Light Side of the Force in Star Wars Galactic Defense consists of the champions of the Galactic Republic and the Alliance to Restore the Republic.
The Alliance to Restore the Republic is used for the first three worlds: Tatooine, Hoth and Endor. While the Republic is used for the worlds of Geonosis, Felucia and Kashyyyk.
The Light Side is opposed by the Dark Side of the Force, on the Original era levels the enemies are from the Galactic Empire. On the Prequel era levels the enemies are from the Separatist Alliance.