Attachmate's layoff almost certainly has nothing to do with the open-source viability of Mono and more to do with the difficulty of monetizing it. MonoVS, MonoTouch, and MonoDroid are fantastic projects, but the commercial demand for each is relatively low. There's probably not as much money there as was once thought.
(disclaimer: I'm a former Mono contributor and occasional user. I have no knowledge of this situation - this is the first I heard of it.)
I really don't know what you are basing you assumption on that most open-source developers dislike Mono, I know plenty that think its great as I do. A lot of pretty cool stuff is happening in the .Net world these days and Mono makes them available to us Linux and OS X developers. The only arguments I have heard against the project has been based on FUD.
Does the anti-Mono crowd just lay in wait for a negative story to further disseminate FUD? I've used Mono a few times and I just do not understand the treatment of Miguel and the project. The only answer I have ever deduced is that Mono is rooted in a Microsoft technology and the anti-Mono crowd apparently hates Microsoft.
ObjC is for Apple only, because - they more or less control the field and push it hard there - other implementations lack the ecosystem - other implementations are far behind
Mono gained quite a lot of traction (F-Spot, Banshee, Tomboy) on Linux, so far that it even allowed to 'backport' former Linux-only apps to Windows and OS X. You get the nice features C# provides, even if you are not on Windows. And you can rely on the same framework.
: Except when you don't: WPF is the biggest example, other areas might lag behind as well. But you _can_ write software for multiple systems _or_ focus on Mono (Gtk#, Mono.Posix/Mono.Unix) only to rapidly write software on Linux.
I think the difference is that OpenOffice is done. It is more or less complete and usable right now (if arguably far from ideal). The Mono Project still many missing pieces (like tools for finding memory leaks or documentation). Compared to OpenOffice's, Mono's situation rides much more how much people expect that it will be maintained, adopted and get "traction" in the future.
That said, I don't know enough to say if Mono is "dead" or not.
Edit: I think this is also a quality of development frameworks as opposed to end-user applications. This is why developers were rightly concerned about the future when Nokia changed its development plans.
OpenOffice is a single application. No one is going to have any trouble using that code base.
The correct comparison is to Java. Oracle is currently suing Google over Sun's patents on Java. And people are fleeing Java in droves. And the language around Mono's licensing of patents is pretty transparently designed to give Microsoft the option of suing people building on Mono.