Fair point. You're not actually VPNing *into* your machine, but into a Hamachi-operated central management server. That has... interesting... security implications, but I suppose it does provide convenience (it would also be an immediate termination offense anywhere I've worked that had a firewall configuration like you describe, but that's your problem, not mine). Why can't you set up port forwarding in the firewall? Also, you did expressly state "Therefore I want to run some VPN server on the machine" where "the machine" presumably means the one behind the firewall...
The only time I've tried using Hamachi before was for "LAN" gaming over the 'net, which I decided not to do after looking at how it worked. That was long enough ago I'd forgotten the details of how it worked.
My first post still stands. There are at least two things Hamachi (or similar) would need to do that are impossible for a WinRT app (or for any software on RT without a jailbreak, really): create a network interface (we haven't even managed that *with* jailbreak, because except in the case of the semi-official driver from Pluggable we don't have any NDIS6 driver we can compile for ARM) and control a network interface from an app (there are possibly some rather hacky ways this could be done, but nothing we have right now).
Win8/Windows RT projects:
List of desktop apps for hacked RT devices
Native Access WebServer and Libraries
WP8 Interop Unlocks
Storage Cleanup tool
XapHandler, Root Webserver, OEM Marketplace XAPs, Bookmarklets collection (Find On Page), Interop-unlock hacks.
Do not private message me with questions that should have been posted on the forum!
Not only are you wasting your time - I'm not going to bother writing an answer to such a question for only one person - but I will probably block you from PMing me in the future as well.