Not username and password no
You need an oAuth token.
- So a user goes to your site.
- Clicks login with Twitch
- User grants permission (with the
channel:read:stream_keyscope) - You get a code
- Exchange the code for an oAuth token
Then use that oAuth token to get the stream key.
It’s not locked to developers.
You only need to have signed up for a client ID then authenticate whomever you need