Think about the ffi annoyances with c->c++->other-lang, its so simple in jruby to use clojure libraries, or rhino for some other stuff, or vice-versa, or whatever.
And I'm not a java fanboy, but that fundamental aspect of the jvm as a platform is crazy cool.
If you're into functional programming the CLR is the runtime to beat.
Except it doesn't run on any useful platforms. Java makes the effort to be consistent and good on a wide variety of quality systems.
Not the mono runtime; the fact that there are two runtimes.
The official MS one, and the Mono one, and although they're kind of compatible, in that your C# can be compiled to run on either of them (mostly, sometimes, if you haven't done anything fancy, if you're not using MVC, if you're not using a UI layer that isn't portable, if the version of mono you're using from A is the same as from B ( >_> unity...) ), this is FAR away from the java JVM, where you can ship an application that just runs on all the platforms.
Don't get me wrong, you can do that with C# too... if you use Mono only, and flip off the official M$oft .Net runtime.
...but the mono runtime is behind the curve, always playing catchup to the 'official' runtime, supporting a subset of the features, and everywhere runs different versions of the mono runtime. It's a mess.
You've got to admit, the JVM is 100% superior in this regard.
To compare Mono to the MSFT CLR and call it rubbish by way of contrast to Java-land strikes me as hilarious. I'll choose .NET every time given that choice...
Only at the very limited level of "versions of the JVM before x have a bug that makes this package not work.
>Or dealt with software that only worked with one very specific version of the JRE that was exclusive from the equally specific JRE required by another bit of software?
No, never. I know one should never overestimate enterprise software vendors, but you'd have to try really hard to make something that crap.
No, never.
You mean two different JVMs, from different vendors? Who uses those anymore?
Really? No one uses Linux? And you're talking about Java and JVMs? That just looks silly.
If there had been a true first party (i.e provided by MS .Net CLR) for other platforms it would probably have had massive traction.
Microsoft can't let go. They can't say "this code is now open and no strings attached". They can say "but not really". They can say "but don't touch anything". Microsoft can't open.
What they can do is okay for consumers. Consumers will download whatever software available and use that. Developers? Hell no. Developers don't trust openness that can be revoked. Because this means their product stops working.
But mono is not .Net. I mean, if you look at Java, there is a very strict process which a JVM implementation must undergo in order to be called Java (and still there are a dozen of such implementations). It means it behaves predictably and have every one of the required APIs. And most of development tools are written in Java.
On the other hand, with .Net we have Microsoft implementation on Windows - and we have everything else. .Net on Windows has a massive number of APIs (many of those system dependent), hatches into COM, can easily use native code and libraries. Most .Net tools only work on Windows and are written as a mixture of native code, bytecode and COM. And mono is a second class citisen forever. It will never have all those limitless APIs and will never have all the tooling. It is extremelly unlikely that developers (of proprietary, in-house, server software) who use OS X or Linux as their development environment will ever adopt it. Nobody likes to be second class. Programming is painful enough even without that.
Whether .NET is different from Mono is not what I argue. Mono brought a MS-inspired technology to Linux so they got under the MS hatred umbrella. There was and still is a purely knee-jerk / emotional reaction to whatever they bring to the table.
Anyway, Stallman is not a good example of vilifying anything. He's the strictest man in town. He is afraid of everything. Rightfully so. But he's not a representative sample of the community.
OTOH lots of people use and love OSS including very profit driven startups and Apple "fanboys". Being able to write C# using Visual Studio under OS X and deploy to Linux would be killer app for a lot of startups and of course whatever stack gets used by the popular startups will be lionised.
Which is something a lot different than an a project actively developed and supported on multiple platforms by Microsoft.
Xamarin is OK, but it's tiny (in resources and reach) compared to Microsoft.