There was a big discussion about this in the Ars Magica forum, that discussed Apprentices when it came out. Matt Ryan specifically stated that he didn't want to limit troupes as to what Hermetic Virtues can be taught. And leaving the possibility that the Gentle Gift can be taught is one of those things. Some virtues (Gild Trained and Skilled Parens) make less sense as a "taught" virtue.
Since this game is apprentice focused, I wanted to allow that freedom. Clement and Kaltheus both have the Gentle Gift. So they can teach it, as outlined in the Apprentices thread. Godfrey can accumulate half of the XP taught in a particular class taught by them into an Ability called Gentle Gift, and once it reaches the necessary SQ he knows it. That SQ will probably at least need to include the major magical focus. The Target level for a major Hermetic Virtue is 21, but will go up and down based on other Hermetic Virtues manifest, and may be reduced by the initial Hermetic Flaw taken when the Arts are opened and any other Hermetic Flaw acquired from either Kaltheus or Clement. Assuming the SQ is 21, it will take 5 semesters to learn the Gentle Gift. (2.5xp/teacher*2 teachers w/ Gentle Gift=5 xp per semester, 21xp /5 xp/semester=4.2 semesters). That's 5 out of 12 semesters.