I don't see why they would. This has been an obvious move for a long time, keeping it closed never really made any sense to me. They gained nothing from .Net being closed except hate and utter avoidance from people like me (vocal early adopters.)
MS doesn't really make money off C# or .Net directly, they make money off the windows licenses you need to run the resulting code.
Open C#/.Net = stronger, longer lasting community / free improvements = more users = more licenses.
It also has other side effects like fostering [more] open source frameworks/plugins for their platform, which again, strengthens their position.
Microsoft also today announced that Visual Studio 2013 has sold over 3.7 million copies since its release less than five months ago. That makes it the fastest-selling release of Visual Studio to date.
Based on those numbers and the fact that Visual Studio prices range from about $1,000.00 for VS Professional up to $13,000.00 for VS Ultimate, I'd say they make quite a bit of money of C#, .Net (and of course C++ as well).
At $100.00 a pop those sales numbers would still indicate VS generated sales revenue of $370.00 million.
My guess is the actual revenue figures are probably in the $1B to $2B (B = billion) range, which isn't too bad for a product that I'm sure Microsoft doesn't consider one of their big money makers and a product line that I'm sure they also subsidise with income from sales of their other products.
I too suspect Microsoft looks at VS as an essential, break even product, but with sales numbers like that I can't believe they aren't also making a nice little profit from VS.
Those sales also include MSDN You can buy VS 2013 right now, without MSDN for around $400.00. Still pricey IMHO. But no where near the 1k price-point you referenced.
Curious, what was so bad about 2012? I could barely even tell the difference when upgrading to 2013, aside from the addition of the nifty Peek Definition feature.
I wouldn't call 2012 terrible, but 2013 seemed a marked improvement to me. Little features and enhancements were sprinkled all over the place. Better Blend functionality is one enhancement I've noticed.
VS has been around a lot longer than C# and although anecdotal I would hazard a guess to say the majority of those sales were at massive discount to schools and universities not to mention there is no way they would get 13k a pop in other countries.
Like I said they dont make money off the language or the framework directly it being open source will certainly not hinder or hurt their vs sales. It will most likely increase them.
Releasing .NET sources could help Mono development and ultimately lead to .NET world not being locked to Windows (at least on servers, you'd still want Windows for Visual Studio when doing development)
Unlike GPL2, the Apache license has an explicit patent grant. When I first saw this announcement, I didn't realize what effect it will have on the patents used to bring up any chance they got: they join the patents already available under various approaches (due to C# standardization or the Communit Promise). And I believe you can now avoid the goofiness of all end users explicitly needing to accept the Community Promise.
MS doesn't really make money off C# or .Net directly, they make money off the windows licenses you need to run the resulting code.
Open C#/.Net = stronger, longer lasting community / free improvements = more users = more licenses.
It also has other side effects like fostering [more] open source frameworks/plugins for their platform, which again, strengthens their position.