I've seen many people programming on Twitch https://www.twitch.tv/directory/game/Creative/programming

While its mainly Game dev or game dev related its not limited to game dev stuff. From their FAQ https://help.twitch.tv/customer/portal/articles/2176641

  Examples of what you can broadcast on Twitch Creative:
  ...
  Programming and coding  
  Software and game development  
  Web development

EDIT: It seems that re:invent is being streamed on twitch anyway.

This is a product announcement, though

And Twitch have had TV Shows streamed on it in the past https://www.twitch.tv/whoismrrobot

My guess that was a sponsored deal or something. But as my edit from before it seems that re:invent is being streamed on Twitch anyway so guessing its all above board (and as others have said Amazon owns Twitch).

Amazon might just let Amazon talking about their products slide ;)

I'm guessing it is covered under the Twitch Creative Conduct, since there is an entire Creative category now that is getting more popular which involves people painting, cosplay, digital art, etc.