Yes it's running on Phusion Passenger Enterprise, we eat our dogfood. We were getting so much traffic that the server ran out of memory and swap. I tweaked some settings and it's ok now.

Awesome, I just bought a license. One question, one license is limited to two machines simultanuously... Is the usage in development (on a localhost) also counted against this limit?

Yes. We have however already received requests for workstation licensing terms. We will discuss this internally and see whether there's a better way to accomodate people who use Phusion Passenger Enterprise in development.

Wait, so the machine count isn't through the honor system? You truly won't be able to run another instance of the server if you have one production and one development server going?

We protect through our license, not through engineering. There is no copy protection implemented in Phusion Passenger Enterprise, so technically speaking, we can't stop you. Instead, we trust that our users won't abuse this fact.