This guest whitepaper explains how hypervisors can isolate proprietary software from GPLv2 and GPLv3-licensed software. Authored by a Trango product manager, it uses Trango's hypervisor as an example, showing how the technology could help safeguard copyright-encumbered multimedia content in a video playback device with a user-modifiable Linux OS component.

The paper was written by Bruno Zoppis, a former Sun Microsystems software engineer who now manages products for Trango. Alongside Trango's “Virtual Processors” technology, Zoppis appears to consider products from VMWare, IBM, and Sun Microsystems as falling into the “hypervisor” product category.

Zoppis begins with an introduction to GPL licensing, including the differences between GPLv2 and GPLv3. Discussion focuses on “anti-tivoization” language in GPLv3, which interdicts locking hardware to the stock firmware — for example to prevent the device from functioning with user-modified firmware.

After acknowledging that Linux itself likely will not move to GPLv3, Zoppis notes that many other open source projects already have. For example, Samba — popular in myriad consumer electronics gadgets because it lets Linux devices use Windows networks — has been licensed under GPLv3 since release 3.2.0. Using GPLv3-licensed software such as Samba could put the onus on devicemakers to open their hardware, a potential liability for devices that handle content vulnerable to theft, such as copyrighted material.

As a work-around, Zoppis suggests the use of hypervisors such as Trango's products. He writes, “In the same way an operating system can simultaneously run multiple applications, with different licenses, the virtual machines that run on the hypervisor do not need to be of the same license.”

Zoppis then outlines a typical use case, sketching out a device that streams proprietary video. Linux provides the UI, networking, and so on, but handles only scrambled video data, handing it off to a proprietary, closed video playback executive via a chunk of shared memory. “The bootstrap sequence checks the integrity of the hypervisor,” Zoppis writes, “but not the GPL VM code,” enabling users to freely modify the Linux environment.

Zoppis probably explains it better than I have; read the whole paper to learn more. The paper is entitled, “Using a hypervisor to reconcile GPL and proprietary embedded code,” and is available here.

—Henry Kingman

 
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