As was back during the launch, the Raspberry Pi is not currently Open Source Hardware. However, Foundation members had made statements that their intention is to release the schematics and board layout. Today marks the first step as the Model B schematics have been posted to the Raspberry Pi Foundation's site:
http://www.raspberrypi.org/archives/1090
Now that there are Raspberry Pi boards in the wild, we thought it would be a good time to share our schematics with the world. In addition to giving you an idea of how the device works internally, these should also provide the information you need to build add-on boards which attach to the GPIO expansion connector and (in due course) the display and camera connectors.
After reading through many Raspberry Pi troubleshooting threads, I think these schematics will really help the community better support those having trouble and identify work arounds for issues that maybe discovered.
From the comments, Liz Upton writes that Pete Lomas, the hardware designer, used Mentor Graphics Expedition to layout the board and that "we do plan to release the PCB designs in the future". However, there is a the practical issue that the Pi is specifically designed for a Broadcom SoC chip which is not freely available for purchase.
The Raspberry Pi is introducing many people to Linux and the open source software ecosystem for the first time, so I look forward to the subsequent publishing of design files so that it can be categorized as Open Source itself.
Cheers,
Drew