Right now the podcasts are only in English, and (I believe) only use English sources. I'm sure this will change soon enough though.

I fed it an Italian Wikipedia entry and it generated a (relevant) podcast and summaries in English, so at least the input seem to support multiple languages even if the output is in English.

If I had come across something like this 2/3 years ago it would have looked like magic, but even now it’s quite impressive.

Edit: You can change the language following the indications in the FAQ; after that, text generation seems to be in the configured language, but the podcast is still in English.

I gave it a book in Japanese that I wrote and it generated an accurate podcast about it in English.