Adult content is not necessarily objectionable by our standards. Straight out pornographic content is not something that we’ve discussed in detail, but is nevertheless not at all what we intend when we say Grossly Offensive. For example, Fifty Shades of Grey and Secretary both came up as something we specifically are not addressing with these guidelines (although Game of Thrones may be). Stories like Fifty Shades might be prone to problem if they include content that is more obvious rape rather than BDSM, but stories that just include sex (even explicit sex) wouldn’t necessarily violate our guidelines as they stand.
N.B. This does not mean we would be certainly able to publish it, I’m unaware of the most explicit text iOS allows, which would probably be the most notable blocking problems, and adult images would present a unique problem in that I believe they would violate iOS guidelines and so we wouldn’t published for unrelated reasons.
Regarding licensing CS for publication outside of Choice of Games (and sibling companies), yes, that is an possibility, although one we generally do not promote or recommend. (We also haven’t done that in quite a while, and so I believe we would have to review the exact term before offering it again, but yes an upfront fee would almost certainly be part of it). It would also require an author to probably know their way around JavaScript, HTML, dealing with distributors (including distributor fees), tech support, and other things that we normally provide.