see
Pedantic Grognard
As a high-level overview (not legal advice for whatever jurisdiction you're in) CC-BY only really requires credit and link. If you release something as CC-BY, I can release my adaptation of that material without putting my adaptation under CC-BY, and I don't need to mark what material in my release was released by you and what is original to me (though I do need to mention that I did modifications). The license forbids me from trying to stop a third party from using your material under CC-BY, but I don't have to particularly facilitate it, either.
In general (though there are some possible corner cases), this means that if I adapt material released under CC-BY, I can release my adaptation under the OGL 1.0a, the ORC, any of the other CC licenses (jncluding -NC, -SA, and -ND varieties), or a wide variety of other licenses.
Looking at the Black Flag SRD, they did what looks to me (in my layman understanding) as the correct CC-BY attribution and link; someone who wants to find out what they can use under CC-BY should follow that link in the PDF. If someone uses something directly from the Black Flag SRD (instead of going back to the WotC SRD with the provided link), they should use ORC.
In general (though there are some possible corner cases), this means that if I adapt material released under CC-BY, I can release my adaptation under the OGL 1.0a, the ORC, any of the other CC licenses (jncluding -NC, -SA, and -ND varieties), or a wide variety of other licenses.
Looking at the Black Flag SRD, they did what looks to me (in my layman understanding) as the correct CC-BY attribution and link; someone who wants to find out what they can use under CC-BY should follow that link in the PDF. If someone uses something directly from the Black Flag SRD (instead of going back to the WotC SRD with the provided link), they should use ORC.