> Does it have to catter to every GUI toolkit there is?
To be a first-class citizen on "the Linux desktop", covering at least both main alternatives is a must.
> Mono developers targeted GNOME.
Thereby renouncing half the desktops.
>Actually the most popular Enterprise choice has been Gnome for half a decade or more
Maybe in the States. In Europe, KDE has long been the most popular choice for large deployments, which is why RedHat and friends still ship it.
So what? It targeted the Gnome desktop. Does it have to catter to every GUI toolkit there is?
>And very few KDE apps.
And no KDE app at all was written with GTK. So what? Mono developers targeted GNOME.
>Except that it simply didn't belong to half the desktops (i.e. ones running KDE, which might actually account for more than half the deployed Linux desktops, considering it's long been the most popular Enterprise choice).
Actually the most popular Enterprise choice has been Gnome for half a decade or more. The only major exception had been SuSE, a distro which languished. RedHat (and Centos), Ubuntu, etc all went for Gnome.