A FastAPI backend used for the server-client version of NUSGet Web, which you can access here (source).
This project is deprecated. Please read the deprecation notice in the NUSGet-Web repo.
This API offers the ability to download any Wii or DSi title from the Nintendo Update Servers. For free titles (titles that have a common ticket available), you can request a WAD or a ZIP of decypted contents. For all titles, you can request a ZIP of encrypted contents.
The legality of this API is questionable, however it should be noted that the remote server does not store any Nintendo-owned data. All NUS content is downloaded at the time of the request, is manipulated in memory, and is then passed along to the client.
The NUSGet API uses FastAPI's built-in documentation, so you can view the available endpoints and their parameters here.