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Sandstorm is an open source package manager for web apps, and it runs on Linux systems. It makes it easy to start up Etherpad (or any other packaged app) with a click. You can read more + try the demo here:
https://sandstorm.io/
Security-wise, it takes the Google Docs sharing model and applies it to entire app instances, resulting in web apps that are private by default, insulating you from app bugs. Usability-wise, it takes 120 seconds to install and automatically updates itself.
This meetup features a talk about the Sandstorm app permissions & sharing model (which for security nerds, is based on object-capability security) by David Renshaw. There are also and a hands-on session to see how to install Sandstorm on a server, and a hands-on session on how to package apps for it. Any web app that runs on Linux can work on Sandstorm.
P.P.S. I'm also sending a note like this to sf-lug; semi-sorry if you see it twice.
P.P.P.S. Sorry for the startup-tastic .io domain name. It really is free, open source software, despite the domain name in the Indian Ocean.