GPLv2's implicit patent license and Dalvik
Posted Jun 6, 2011 21:38 UTC (Mon) by FlorianMueller
Parent article: Android, forking, and control
I believe the following claim oversimplifies and probably overstates the scope of the GPLv2's implicit patent license:
Had Android been built on Oracle's GPL-licensed Java code base, there would have been no suit; Google would have been protected by the GPL's implied patent license.
I don't doubt that the Android team wants to avoid the GPL wherever it can. I also don't doubt that the GPLv2 does have an implicit patent license, and that it has significant scope. But I don't think one can just assume -- given that there's no case law on the scope of the GPLv2's implicit patent license in any major jurisdiction that I'm aware of -- that Google could have built Dalvik safely on a GPLv2 basis, given that Dalvik is architecturally quite different from Java (executing DEX files, register vs. state machine, etc.).
An implicit patent license undeniably covers those who use code that was published by the patent holder and never modified. In connection with the GPLv2, one can certainly argue (more or less successfully -- unfortunately no case law yet) that some modifications to that codebase are covered. But there must be a limit somewhere. If someone changes a codebase beyond recognition, there will be a point where it's at least risky to rely on the implicit patent license. And if completely new code segments are added, it becomes very difficult to argue that the implicit patent license still applies to any use of the implicitly-licensed patents by such additional code (the European Commission's DG Competition is pretty sure such use of patents is not covered).
Given the aforementioned architectural differences between Dalvik and Java, it's hard to see how Google could have built Dalvik without pretty fundamental modifications to any Oracle/Sun GPL-licensed code as well as major additions.
Even GPLv3's explicit patent license has limitations. If the FSF had believed that the GPLv2's implicit patent license goes beyond the scope of the GPLv3's explicit patent license, GPLv3 would have been counterproductive in connection with the most important issue for which it was created -- patents.
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