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.

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.