There's an official Espruino board, but there are also compatible boards that you can use. The Espruino firmware can be installed on the other boards manually, so if you've already dabbled with microcontrollers you should be able to get a compatible board loaded up and ready to run. The Espruino hardware reference has more details.
The Raspberry Pi has some IO pins (the GPIO connector), but microcontroller-based boards like the Espruino use much less power. That means you could leave a board running on batteries for a significant amount of time.
The project was successfully funded on Kickstarter, where they raised £100,710.