Here is an alternative reality that might had been much better for him and the world:
- Bill buys and Open Sources Windows XP code
- In the short term Microsoft would still be the leading expert and driver on Windows XP development since it is the one with the best engineers and knowledge about how it worked
- There would be a much cheaper version of Windows available to large parts of the population (you know, those billions that still don't have access to good technology)
- There would be a cottage industry to maintain Windows XP (including stability and security patches)
- There would be much more scrutiny and review of Window's XP code base, and a number of Security vulns would had been discovered sooner (in the case of this code base, there would be a LOT of eye-balls looking at it)
- For the next versions/releases of the Windows OS, Microsoft could not depend on the 'forced upgrades' and would really had to compete properly with Windows XP (see Microsoft should sell Fully Patched Windows XP licenses (or open source it))
- I think that Microsoft would be very successful at this, and would still be the main driver of the (now) Open Source version of Windows
- Microsoft would still be able to charge for Windows, since most corporate/personal customers would still want the 'Microsoft version' (which would be certified and maintained)
- Remember that the first versions of Windows (and Microsoft products) were massively copied (or 'pirated' depending on the point of view) which helped to create an environment where most users and developers knew how to use and program Windows (i.e. a big part of Windows' success was the fact that it was everywhere (with only a smaller percentage of those installations actually paid for))
- There would be HUGE innovations driven by using the Windows kernel and OS in all sorts of devices, and who knows what would happen in the mobile space (remember that Window's Kernel and Win32 APIs are really mature, with lots of knowledgeable programmers around the world that would be able to expand it and adapt it)
- Driver support would be much better since the manufacturers would had much better access to the windows source-code and would be able to develop much better solutions.
- I don't think that disasters like Windows Vista and Windows 8 Metro UI would had existed
- in fact I think that a number of UIs would appear, and the best one would eventually emerge
- maybe Microsoft would develop Metro as a paid 'add-on' which would sit on top of the existing windows (and be compatible with multiple version of windows). Of course that this version would really had to 'work' and make sense to users :)
- An Windows App Store that allowed developers to sell apps that run on windows would exist by now (this would be there for Microsoft to lose, since again most users would prefer to buy from a trusted brand)
- Think about the innovation in new Languages and Development IDEs that could had occur under such vibrant eccosystem
- Remember that Microsoft and its ISV partner network would be putting a lot of energy and development into solutions build on top of the new free and open OS
- The other (non Open Sourced) Microsoft products would had to step-up their game and not rely of the fact that they had direct access to the windows OS (vs their competitors).
- I think that this would had done wonders for these teams, would had 'forced' them to collaborate more and maybe the whole 'One Microsoft' would had arrived much sooner
- Note how Azure become such a great force by not playing the 'Microsoft only' card and supporting the best of the currently available technologies (which of course also had the massive positive side effect of exposing the internal Microsoft teams to what was happening in the 'real world')
- Ironically, this positive change of culture would probably be the biggest advantage for Microsoft, since it could really put Microsoft on the leading edge of technology culture and be able to recruit a huge amount of talent (that would be attracted by the 'open culture that Microsoft would had to become')
- Note that these type of 'open culture' can't be fudged, which means that either the top management of Microsoft really believed and 'got' how Open Source really means, or this strategy would not work
- In terms of Microsoft's Stock Market price, I don't think it could had gone much worse that it has since
- There would be a massive reduction in EU and US anti-competition regulatory issues/demands/problems.
- Microsoft would had been in a great position to counter Apple's closed culture, and be able to have a really strong foothold in the area that created Microsoft's power in the first place: Developers who wrote killer products/apps for Microsoft's technology stack
- Maybe the .NET crowd would had not lost the battle to become a strong Windows App Development environment (remember the big plans for a managed File System, Network Stack and even OS), and Application Sandboxing was finally possible in windows (I still believe that Managed applications are the only way to really enforce CAS (Code Access Security) policies, and to have a hope to be able to control what an application is able to do to the user's data, applications, network and OS)
- The Raspberry PI revolution could had started much sooner (remember that the Raspberry PI processor is probably as powerful as the computers that were powering Windows 2000 and XP 12 years ago)
Bill Gates had the money to do this (in fact he still does), and can you image the innovation that would had occurred, and how many lives would had been changed, if a much wider part of the world population had free and open access to such a mature and powerful operating system that Windows XP was?
Just think about the medical devices that could had been created and deployed? (and Medicine, is just one of many industries that would had benefited from such free and open Operating System)
Ironically, I'm pretty sure that even if Bill had bought the Windows XP code for a massive pile of money (or stock), he would still had enough to spare to spend on the other philanthropic activities he is now famous for (i.e. he could had done both)
Of course that on this reality Bill would had to really understand what Open Source really is, which is something that unfortunately I don't think he has even today.