Thank you kindly for your explanation and the additional resources. In the meantime, I also read some articles on Fanlore and on the Podfic Resource Site, and that really prompted me to think about it and write mine. I'll also share these with friends in my fandom, I think these are important practices in communication with other people in fandom. From my experience, my fandom on Twitter did not adopt many of the practices here, which makes it more "use your common sense" and more immediate on one hand, but then it also hinders a lot of other good things; it would be good at least to have the choice to opt for this solution. So again, I do appreciate it.

I agree that "Blanket permission" may lead to misunderstandings for those who are not in the know. Transformative works policy is much clearer to me.