Piston is one of my favourite apps for Django ever. I have used it in many projects and it worked just brilliantly. My compliments for making such a beautiful library.
Now about the issue. Today, I wanted to use it for a new Django 1.5 project and was surprised that it just didn't work. So pity. I had to build a simple API myself (including security verification and other things I would rather have delegated to Piston).
Please, update the Piston for Django 1.5 and keep up with great work.