I'm not sure those two statements are related. I don't see how having .NET open sourced is directly effecting Microsoft's bottom line. I like getting free stuff too, but that doesn't man it is necessarily profitable for the company.
IMHO, it's the "open" part and less the "source" part. I believe a lot of projects were reluctant to jump on the Mono train because they expected it would be steamrolled (on purpose or just through sheer manpower) by the .NET. However, if everyone is building on top of the same CoreCLR, it's possible that fear might subside. I doubt it will ever go away because Microsoft will continue to keep some APIs close to the vest.
If it's possible to transpile either Java source or better Java class files to a CLR assembly, even some of the community momentum that Java has might turn into a benefit for .NET, too.
I had heard of such projects back in the day, but didn't know if they were still in service (and I didn't take the time to research it). I had some skepticism about whether IKVM had kept up with the rapid moving target that is the JRE, but after seeing that it runs Minecraft[0], I'm guessing it'll likely be alright :-)
But holy shit, who in their right mind still uses CVS?!
First of all, it's not just opening up .NET. It's also many other cool things Microsoft has been doing: Linux on Azure, TypeScript, etc. etc.
Regarding .NET, it is likely it will benefit Microsoft significantly. First, because Microsoft would not do it without strong reasons. Second, we can guess at those reasons: Microsoft wants to grow its developer ecosystem. .NET has been limited due to being Windows-focused. Opening it up makes sense.
(Yes, Mono exists, but the .NET cross-platform experience still wasn't good enough. Not necessarily Mono's fault, but regardless, opening .NET can solve this (possibly at a cost to Mono).)
