Windows basically works now, built with Visual Studio 2012. I just got done packaging the app into a Windows service so it can run properly in the background instead of from an admin console window. I've also built the Qt GUI for Windows and it works well too. There are two remaining Windows issues:
1) Auto-update on Windows. I finally found a good free MSI packager that is good enough, but I will need to test. I will also need to figure out the update dance. On OSX and Linux the app can download the update, verify it against the list of authorized update signing certs, and then exec() the update in place. On Windows the service has to execute some kind of intermediate, die, and then the intermediate has to run the update and then start the service again. Annoying... more moving parts, more to fail.
2) The Windows version takes care of automatically installing instances of the tap driver, which is a fork of the OpenVPN tap-windows driver with some extra ioctls that I added to support a few things ZT1 needs and Windows does not provide. That is working and the tap driver is working, but there are still some rough edges around what goes into the registry to configure the tap devices properly so that they look right in the native Windows network connection dialogs. I want the user to be able to use those dialogs too to do things like set firewall policies on a per-tap basis and have those settings stick.
3) I want to make sure that these connections are by default treated as untrusted networks by the Windows firewall, for obvious reasons. If the user wants them to be considered trusted they should have to go into the Windows network connections dialogs and say so.
I'd say ETA about a month for Windows since once those two things are nailed down I will want to do a few weeks of my own testing and let auto-update run several times in various VMs. You can try it right now on a Linux cloud server or in a Linux VM if you want.
BTW, Windows 7 and 8 will be supported. Vista will probably work too but I'm not sure if I will "officially" support it. Windows XP will not work since it is missing a number of core networking functions that this app needs. But XP is ancient and EOL anyway so that's probably okay. It's open source so if someone *really* wants it for XP they can port it and contribute it via GitHub.
Congratulations on your release, Adam!
I use a Win7 machine, so I won't be able to test yet. Is there an ETA on that package?