Sony had, a long time ago, a family of Unix workstations. At that time, those systems were called "open" in the sense that they played well with other systems over documented protocols.
Quoth the raven: SNAP is a completely open-source licensed (for license details click here) development environment based on GNUstep.
Historically, GNUstep is based on the OpenStep specification developed by NeXT (now Apple Computer Inc.) plus additional extensions added by Apple through the Cocoa framework. SNAP is an extension of this framework created by Sony and will take a big step forward in evolving a new application framework.
The initial areas of enhancement target the windowing system and graphic framework but further modifications and refinements address networking, widgets, UI building, 3D graphics, file system, garbage collection, performance and execution size. The overall goal of the SNAP project is to develop and evolve a next generation native application framework for embedded devices. While SNAP does not currently target a specific hardware platform or product, the long-term goal is to enable SNAP on Consumer Electronic (CE) devices.
I loved the hardware of a Sony MP3 a bought a couple of years ago but it was ruined by absolutely atrocious syncing software. I hope this means they open up their interfaces a little more and let other people integrate with their products.