Well that's a bit over the line. I would not call it a joke. I do not see a problem with using BTC (spending wallet) on Windows as long as proper security measures are set and the user has experience/knowledge. As Vod said, currently most people are using Windows 7 but a surprisingly high amount is still using XP. Windows 8/8.1 is okay, but Windows 10 is horrible for BTC.

Ubuntu is a Debian-based variant of Linux with unity as it's desktop environment. Aside from computers they're trying to migrate the OS to smartphones as well. Ubuntu is free as well.