The ten commandments reference would most likely suggest a comparison to rules or guidelines for behavior. It may be used to emphasize how egregiously someone has erred, by showing that mistake in a biblical context. It may also show that mistake to be one of morality or ethics, as opposed to a simple issue of legality. Any biblical allusion in this novel will emphasize the idea of Finny's fall from the tree as a sort of "fall from grace" for Gene-a re-imagining of original sin.
Finny is the innocent in the novel, the one who truly cares for Gene and seeks his friendship Finny is incredibly easy-going, and several skills, including athletics and social skills, are remarkably natural for him. Others, like academics, are not so natural, and require great work to produce mediocre results. Finny is open & honest, and refuses to believe that Gene could betray him in any way. It is his gradual realization of this fact that leads to his second fall and tragic death.
Gene's character can be interpreted many different ways. I personally think of him as a sociopath. He continually acts without regard for consequences, and convinces himself he does it all for Finny. The first few chapters, where he jumps from describing Finny as his best friend, fawning over how lucky he is, to a kind of paranoia bordering on sinister really highlight his fragile state of mind. However, others see him as a boy overcome with adolescent jealousy, unable to cope with the success of his roommate.