“By 2025, more than 50% of desktop computers in the world will be running an open-source operating system.”

The open-source development model has proven to be vital and robust. Many thousands of developers around the world have cooperated to build open-source systems containing millions of lines of code.
Companies may rise and fall, but by its very nature open-source software can never go away. I do not believe that any company controlling a proprietary closed-source system can, in the long run, outcompete the global open-source development community.

Open-source software has numerous advantages for users: it is free (as in beer), its design is transparent, it can be extended easily, and it tends to be relatively secure.

Linux and other open-source operating systems have historically seen strongest adoption on servers, but have made tremendous strides in recent years in usability as mainstream desktop computing environments. User-friendly Linux distributions such as Ubuntu are already more than adequate for most computing tasks which most people need to perform.

The main barriers to widespread adoption of open-source computing today include (a) the inertia of a large installed base of proprietary systems, especially Windows; (b) limited support for open-source operating systems from hardware vendors; (c) resistance from content providers who want to control copyrighted content via digital rights management, which is hard to implement in an open-source system (at least without hardware support). These barriers are significant, but I believe that the benefits of open-source systems will ultimately overpower them.

Much growth in computing in the next two decades will likely take place in emerging markets including China and India, where economic incentives will likely further encourage the adoption of open-source platforms.

Definitions:

By a desktop computer, I mean a computer in any environment (home, office, school) used primarily for interacting with a user. I include laptops but specifically exclude cell phones and other mobile devices, as well as computers used primarily as servers.

By an open-source operating system, I mean an operating system in which over 50% of the code is open source, including libraries and applications included in a typical baseline installation. For the purpose of this prediction, I consider software to be open source if it meets the first three criteria (free redistribution allowed; source code publicly available; derived works allowed) of the Open Source Initiative's Open Source Definition (http://opensource.org/docs/definition_plain.php, retrieved 11/23/2006). By this definition, Linux, FreeBSD and Solaris are examples of open-source operating systems today. Windows is not. Mac OS X is not: although the core Darwin system is open source, most other system components including most user interface code are proprietary.