So David and Jonathan come up with a plan in which David will go away, and Jonathan will see how Saul reacts to David's absence. Jonathan and David both promise that whatever the outcome of this test, they will always be kind to each other, and to each others' families.
Saul ends up shouting at Jonathan: "Thou son of the perverse rebellious woman, do not I know that thou hast chosen the son of Jesse to thine own confusion, and unto the confusion of thy mother's nakedness?" I think this is a very suggestive verse, but not in the way that the SAB is suggesting. Take the Bible as a whole and ask yourself: What does the phrase "thy mother's nakedness" really mean? If you look to some other verses, you'll find that the Bible forbade, for instance, a man to have sexual relations with his father's wife:
Lev 18:8 The nakedness of thy father's wife shalt thou not uncover: it is thy father's nakedness.Now, I may be reading too much into it, but it seems that if "thy father's nakedness" is your father's wife, one could easily make the claim that "thy mother's nakedness" is your mother's husband. Saul seems to me to be saying that Jonathan has, in his allegiance to David, forgotten that his true allegiance should be to Saul, who after all is his father. I'm having a hard time putting this into words properly (and delicately), but I think Saul is being very poetically vulgar here and insulting Jonathan on many levels suggesting:
1) "I'm your father, and your allegiance should be to me."
2) "I'm the king, and if you hope to be king someday, you'd better not be supporting David."
3) "If you're going to be unable to get these facts straight, you might as well just have David #$%@ your mother, you little ingrate!"
In any case, this is a harsh rebuke indeed, and Jonathan finally realizes how incredibly hostile Saul's feelings towards David truly are. So he goes to David and tells him that he ought to leave, and they say farewell with a kiss, which once again, is totally acceptable between two straight men in many cultures.