At thefourthvine's suggestion, attention podficcers: If you want to podfic any of my stories, go right ahead - no need to ask permission. Just please link back to the original story when you post your work, and let me know where it's posted. The same goes for visual art, mixes, or any other creative or transformative works you can think of, other than anything commercial.
One exception: please ask my permission via email if you want to write a fic of your own that is somehow linked to one of mine. If you want to continue a story of mine in the form of a sequel, I will probably say no - if you want to write a timestamp or something else small, I will probably say yes. Thanks!
If you're a student or an academic doing a project, feel free to reach out, but please be aware that, due to the stigma associated with fanfiction, and the troubled history of academics studying fandom, I scrutinize academic requests pretty closely. I will generally decline such requests unless I feel assured that my privacy will be protected, that the researcher/teacher has a well-thought-out plan that evinces an understanding of academic ethics and seems likely to contribute meaningful insight about the world of fanfiction, and just generally that I feel comfortable with the person making the request.
If you're a teacher who wants to assign my work for a class, I can't stop you, but to the extent my wishes matter, my preference would be that you not do so. I want my work to be read by people who want to read it, not those who are made to, and I've heard enough of other fan authors' bad experiences with interactions with students who aren't part of the culture to be leery of such interactions.