Come and help us add other authentication options to Outline ;) I can promise you it'll be easier than "whipping up your own"
The issue with All Rights Reserved means lets say I were to put a ton of work into Outline and I want to monetize the work I put in to provide easy hosted solutions. I can't. I'm not saying I want to monetize but I don't know how much effort I will put in and then may regret giving you so much free code.