Hey @andy-6391, first of all welcome to backstage! 
There‘s a SDK available on Github:
You can also find a bit of a „intro“ to it here:
And the product should be available right away.
- either directly from Polyend: Endless • Polyend
- or from retail chains like Thomann or Sweetwater
As you are a dev. I think the best thing to know for you would be that the SDK is just an abstraction layer on top of the firmware/hardware of the device.
It exposes the most important parts (main loop, buffer and user input control) but doesn‘t offer full/indepth control over the hardware, unless you go all the way in and write your own firmware from scratch of course 