Does support multi-tenancy?

Yes, any running Factor app just needs a single node process.

I'd need to know more about specific use cases as multi-tenancy works a bit differently in the Node world than the traditional LAMP stack (WordPress) world.

Of cource we could run multiple node processes, but the question is about supporting multi-tenancy on a application level to be able to scale the app elasticaly and use cost efficiently. For example, you have 2 instances or 2 node processes to handle 10 tenants and you could scale-up or scale-down number of instances based on load. Usually, on a db level every record has some tenant identifier and application level code could handle it transparently.

Ah i see.

We've done some work in this regard, the themes site runs three apps on one process.

Ive had this request a few times, id need an example use case to work through to make it work perfectly though.

I'd like to host a few websites for myself and friends. I'm a JS dev, and would like to use it full-stack if possible, rather than use Drupal or Wordpress.
I've got a little dedi for hosting, but would like to save resources by running a single ghost process that can answer for all of these domains, rather than having to start 5 separate ones. I'm not sure how it would be accomplished in Ghost, but in Drupal, each website has a set of folders that contain any overridden templates or custom files, but all of the core files are shared amongst all of the tenants.
That would be my use case, so hopefully it's possible!

Definitely understand the need. I'll take a look at this in the next weeks; see what's missing. Shouldn't take much.