Mono = .NET framework implementation for *nix.
Wine = Win32 emulation for *nix.
*nix = Linux and Unix in every flavour there is.
Linux was not created because the unix'es where not following a standard or something. Linux is Linus Torval's idea about software free for everyone.
Linux refers to the kernel, the heart, of the Linux 'Distribution'.
The Linux distribution is a set of packages around the kernel. Fedora / Ubuntu / SuSE / etc.
Which distro you use comes down to personal preference. There is no better Linux. Just different.
A Windows user is used to boot from cd, set some install options and after installation, boot into the new system and configure everything visualy, preferably with wizards.
A Linux user does more or less the same, except that all configuration is done in text files, and mostly without wizards. Better yet, you don't need the system overhaul of a window system, and can do everything in textmode.
So the main difference is that on Windows you get away with not knowing the details about what you are doing, since most wizards can do the basic stuff without help. On Linux you need to know each and every configuration option, and the way programs relate, in order to configure it.
Kinda compare to DOS, except that DOS couldnt do 1/100 of what Linux can do, and DOS provided a very limited amount of commands to play with compared to *nix.
So when you decide to change to Linux in one form or another you'd need to read up. When you get the hang of it (I did that in about 4 months) you never want to change back, except for gaming, which sucks on Linux.
There are a few games ported, or compiled by the game companies for Linux, and this number is growing. The ones that work, run faster on Linux in my experience. But it's just no fun playing Railroad Tycoon 2 gold and some arcade stuff when you are used to America's Army or some other shooter.
On the other hand, a quick visit to
http://sf.net would reveal a TON of free opensource software, for all tasks you would ever want to do on a computer. Free!
WINdowsEmulation does a decent job of running (nearly) all non directx Win32 apps. You could Wine Windows if you want to.
MONO =
http://www.mono-project.com/FAQ:_General
Yes, C# is used on MONO.
You would still have to wine RunUO's server.exe on a MONO-ed Linux box. This doesnt make for great stability, cuz you emulate a windows environment for the server.exe to run in. Unless the RunUO server is compiled for Linux offcourse, which will probably be done if MONO is ready enough for the RunUO server to run.
The stable option would be to run VMWare on one of those boxes, and install a Windows machine in it and run RunUO on that. You'd probably need to recompile the kernel to add vmware support, but that's easy nowadays with the aid of faq's and howto's.
Regarding RunUO... I was under the impression that they are opensource asswell ? At least the core is. The rest is copyrighted scripts that you can alter yourself :/ I don't see any problems, but those being created.
So everything that is bugged, could be fixed by the user, provided he (or she) has enough knowledge to do it.
Hope this helps,