I was asking myself that a moment ago and had to navigate around a bit to get a better idea.

Sandstorm is a self-hostable web productivity suite. It is also a marketplace for components that fit within the suite. It has strong ideas about security and the post's linked page is about how they are making that security model available to versions of Linux that don't support some of the Linux kernel's newer features.

Also, it uses Linux containerisation features, like Docker does. But is quite different to Docker:

https://groups.google.com/forum/#!msg/sandstorm-dev/_I7cHARM...

You could click the logo in the top left and find out.

https://sandstorm.io/