This article is primarily about the CodersForSanders organization (https://coders.forsanders.com/), which started on reddit at /r/CodersForSanders and uses Slack to coordinate efforts among over 150 developers, designers, and digital/content folks. I am a member; I built the donation app mentioned in the article (an iPad app for volunteers to collect donations at campaign events using Square readers) and a few other projects.
Regardless of your political leanings, I've found CodersForSanders to be a fascinating experiment at the intersection of grassroots political organization and remote development/tech work. We have worked on projects that campaigns would normally only entrust to expensive consulting firms, but both out of financial necessity and a commitment to grassroots support we have taken on a lot of that work. I wonder if this can be a new model for political organizing in the 21st century.