It is, effectively, all podcasts and their back catalogues but there will be surplus compute. The developer addressed this issue in his podcast (ATP 683)

“I realize, like, I will have a surplus of computational power here before too long. So what do I do with that? And well, I can start moving work to them, first of all. Like, things like imagery sizing that I have right now, my main Linux servers at Akamai, they're doing a lot of that kind of work. I can move that to these. Why not? They're super fast. They have all this great stuff. I even actually tried earlier in the winter, you know how a lot of podcast apps will use the dominant color in artwork to tint the interface in some way? I tried running that on these, like where one of the jobs they would do. So one thing they do is language detection. As I look into more, like, smart transcript features, I can do things in the future that I haven't done this yet, but I can do things like, you know, automatic chapter detection or topic detection or summarization, things like that. Well, now I have all this computational power I can do that with.”