I wonder if you'll be able to put Firefox OS on these. I've been wanting to play with that OS but the current devices offered for it are very underwhelming to try and push its limits.
The 1.1 release was a huge upgrade, but they still have some ways to go. There are problems with the HTML5 Canvas element and positioning DOM nodes/scrolling.
In my experience, it's not straightforward. First you need to install an update from ZTE to unlock fastboot. Then you'll need to compile 1.1 on your own, and flash it yourself. I'm hoping ZTE releases an OTA update, but I'm not holding my breath.