WiinUPro is still in development but WiinUSoft is available.

WiinUPro is a program that allows you to use your Nintendo branded Bluetooth enabled devices with your computer.
With it, you can use your Wii U Pro Controller, Wiimotes and extensions as input devices to play your PC games.
The name derives from an odd combination of Wii U, Windows, and Pro Controller (I pronounce it like win-you-pro).

WiinUSoft is a like a lightweight version of WiinUPro and doesn't have all the same features.
It only allows you to map controller inputs to that of an Xbox 360 Controller for Windows.
It is designed to meet the needs of the majority and is sufficient in most use cases.

The initial focus of WiinUPro was to give users the ability to make full use of the Wii U Pro Controller's analog joysticks allowing precise control in games that support analog input; for example, controlling how much your car turns or how fast or slow your character moves.

The latest beta version of WiinUPro provides the following features:
  • Map controller inputs to the keyboard, mouse or virtual joystick.
  • Turbo features to mimic rapid button presses.
  • Shift assignments to allow you controller to have up to five different assignment layouts.
  • Create, save, and share layout profiles for all your favorite games.
  • Connect and use multiple controllers.
  • And more

The latest release version of WiinUSoft provides the following features:
  • Map controller inputs to XInput (Xbox 360) controls
  • Force Feedback support and intensity control
  • Use up to 4 controllers at a time
  • Create and save profiles
  • Supports all major Nintendo controller types

Currently, WiinUPro and WiinUSoft only supports Windows platforms and is known to be working on Windows 7, Windows 8, and Windows 10 but more supported operating systems are planned to be looked into. I also suggest looking at the FAQ before getting your first Pro Controller if you haven't done so already.