Odysseus and Calypso

After remembering the class discussion we had on Thursday, I went back to the part of The Odyssey when Odysseus was with Calypso. I felt upset when Odysseus stayed with Calypso for so long. I supposed he had no choice, since he didn't have any boats. Even though, wouldn't he still be commiting adultery towards Penelope? That would be an act of unfaithfulness. It surprised me that he still chose Penelope over Calypso at the end.