It is just the software. You get the software and a USB dongle that acts as the license key for the emulator.

I used this back when I worked at IBM. Most people just ran it on a ThinkPad running Linux. I ran it on a rather beefy tower system, as it was slow on the ThinkPad.

We called the tower system, the baby z, and I took it and physically placed it inside of our System z. One day our CE asked why there was a tower inside of the System z. I told him that it was pregnant.

I think the $900 is just for the z software. For zPDT you need to provide your own hardware/cloud instance, and pay for the emulation software on top of that. That came in around $2.5k/year IIRC.