VLC's donation is not for an ARM version at this moment. That means that it will not run on your Surface RT.
They say that they are going to work on a Windows 8 version (x86/x64) first, but then hopefully they'll be able to get a Windows RT / ARM version. On top of that, they're not sure that they will be allowed to put an app in the store with the API calls they use.
In other words, only donate to VLC's Kickstarter if you want to, don't do it with the expectation of getting VLC on your Surface.
Now, there are two different applications that will play MKV on a Surface RT that are already in the store. The first is mobile.HD. This one has a really good interface, but has crashed on a couple of my MKV files (files that only contain the supported Dolby Digital audio, by the way). It also doesn't seem to play files that use AAC audio, in addition to the mentioned DTS. The biggest downside though, is that it doesn't support the "Devices" charm, for support to Play To the 360.
The second is PressPlay Video, which added experimental MKV support in a recent update. This one has been more stable in playing my DD and AAC MKV files. It also does work with the Devices charm. However, it still doesn't support DTS audio, and more importantly, it has an annoying one-time preprocessing step that must be done for each video file that you play (until it saves a few MB file for each video).