A particularly relevant OGL product for this thread is the d20 Book of Erotic Fantasy. Its converted and updated/expanded from the AD&D Complete Book of Unlawful Carnal Knowledge. As a DM, it answers all my questions (including some I would never think of far less ask) about adjudicating a campaign with mature themes.
Even though some of the entries were off-colour (a shock threshold thing, I'm sure) I found the Book of Erotic Fantasy much less confronting that the Book of Vile Darkness, which is a 'canon' supplement.
Nihil est ab omni partum beatum.
(Nothing is an unmixed blessing)