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When to mix proprietary code with Linux

Bruce Perens, co-founder of the Open Source Initiative, takes a break at LinuxWorld to talk with us about open source issues of the day -- licensing, lawsuits and enemy lines.

The possibility of lawsuits against open source by large companies remains a real and viable threat, according to Bruce Perens, open source expert and evangelist.

Perens is series editor of Bruce Perens' Open Source Series (Prentice Hall PTR) and vice president of developer relations and policy initiatives at SourceLabs Inc. He sat down with at LinuxWorld Conference & Expo in Boston this week to explain several sound strategies for combining the Linux kernel and proprietary software and told us why proprietary manufacturers should be concerned and just who the enemies of open source are. What are some ways to mix proprietary software and the Linux kernel?

Bruce Perens: Try to view this in the context of a cell phone, where the cellular provider wants to protect the way they handle the network from open source. In a phone like mine, there are actually two CPUs, so they can put everything they want to protect in the embedded CPU and put all of the open source code into the other CPU. Physically, they're both on the same chip. The General Public License (GPL) would allow that coexistence and permit the interface between those two chips. If it's a well-defined interface then it can be considered a perfectly legal demarcation between proprietary software and open source.

Now, if you look at the license text that comes with the Linux kernel, there's a special preliminary to it that re-asserts that user-mode applications are OK. They are not affected by the GPL license unless they actually incorporate a GPL file. The license of the kernel does not affect the application.

If that's true for the kernel in an application, it's also true for a kernel on top of another kernel. One strategy that has been used successfully in the past by IBM is to host the Linux kernel on top of another proprietary kernel, which, in itself, contains some proprietary device drivers.

Invidia's strategy is interesting since it's the shakiest one. I'm not sure if it is legal. Invidia [Corp.] has made a single loadable module for their graphics kernel, which makes the graphics card work. That loadable module is operating system-independent, meaning that it runs on Windows and Linux. In addition, they have a GPL portability layer that makes that loadable module work with Linux. So it would be more difficult, given that it works on multiple operating systems, to establish in a court that it was actually a derived work of Linux.

Finally, another way to mix proprietary software and the Linux kernel is to put whatever you need to be proprietary in a user-mode application, rather than in the kernel. It is possible to expose the I/O boss to a user-mode application. You don't necessarily get the real-time services you get in the kernel, but for many people, that doesn't matter.

There are, of course, more elements than what I've listed.

Why would you say Invidia's strategy is the shakiest?

Perens: Invidia's strategy is the shakiest because it's a loadable software module that inserts into the kernel. Thus, there is not a 'bright line,' as lawyers say, between the GPL copyrighted pieces and the other elements. There's a very fuzzy line in that case.

Invidia has actually strengthened their case and made it easier for them to win by making that module system-independent.

Do you think it would be realistic to worry about patent issues?

Perens: I'm not the only one worried sick. Every small and medium-sized proprietary software manufacturer who understands the problem is concerned because they're on the bottom. There are some other people who can, essentially, dictate terms. If we get additional software patents and standards, for example, you get a situation where Microsoft or IBM can implement a standard without a patent tax. Small-sized companies might have to pay that tax and their potential for profit would be limited. The problems in patent quality only exacerbate this.

It's a bad deal and it is to the benefit of the largest companies in the world, not anyone else. Everyone should be worried in the software business. Even users should be concerned because this is going to close out their options.

Will we have the so-called 'nuclear option,' where, some day we get up in the morning and read that a thousand patent suits have been filed against open source? It's still perfectly possible and it's bad news for small and medium-sized proprietary software manufacturers too. Those companies are 80% of their sector's economy.

You don't think the GPL 3.0 will take care of patent concerns?

Perens: It wouldn't address them for the proprietary companies at all. Not everyone is using the GPL 3.0, and there's always litigation. You never know how much the judge is going to buy. The GPL 3.0 will help us with our friends -- but not our enemies. Our enemies aren't putting software under GPL 3.0.

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