In what way does Calypso accuse the gods of a double standard?
When Zeus sends Hermes to Calypso to deliver the news that she must release Odysseus from her island, she "burst into a flight of indignation." She accuses the gods of having a double standard having to do with gender: male gods are allowed to take mortal female lovers, but female goddesses, on the other hand, are not allowed to take mortal male lovers.
She provides several examples of female immortals who have been forced to part from their male mortal lovers. In fact, those male lovers are often dramatically killed by the gods. Dawn took Orion as her lover, and the "gods in [their] everlasting ease were horrified," so Artemis attacked him and "shot him to death with gentle shafts." Further, Demeter took Iasion as her lover, but when Zeus found out, he "blasted the man to death with flashing bolts."
Now, Calypso has saved Odysseus from the ocean, and she feels that the gods are targeting her "for keeping a mortal man beside [her]." She feels that it is incredibly unfair that the gods have no problem with keeping their own mortal female lovers, but for some reason, female goddesses are not afforded the same privilege.
In Book 5, Athena asks Zeus to intervene with the obstacles that are deterring Odysseus from getting home. Zeus sends Hermes, the messenger of the gods to go to Calypso's island to tell her to let him return to Ithaca. When Calypso hears of this, she rants on about the male gods, and how they interfere with the happenings of the female gods. She doesn't understand why they are allowed to take human lovers, while the female goddesses are not. However, Zeus wins in the end, and Calypso supplies a boat for him to leave the island.