I'm looking for a library like the one used in this project: keyboard.
Unfortunately, it's only compatible with the Due, so if anybody could tell me about any library compatible with the UNO, that would be great.
Your link to http://keyboard is not good.
If it's really a USB keyboard, you need some additonal hardware - a USB host shield.
The Uno is only a USB slave.
Sorry, copy and paste error.
http://practicalarduino.com/projects/virtual-usb-keyboard
CrossRoads advice is still the same..
only boards like Leonardo/Due..etc are capable of acting as a 'direct connect' USB keyboard..
if you still want to use the UNO.. you'll need a USB host shield.. 
xl97:
if you still want to use the UNO.. you'll need a USB host shield..
According to that link the question is how to make the Arduino emulate a keyboard, not how to make it receive events from a keyboard.
There are plenty of examples on the internet of people who have used an Arduino to emulate a keyboard, including some that were implemented on a UNO.
thanks
The link provided by Op references rancidbacon's V-USB library for Arduino. I've played around extensively with his lib on UNO as well as the original code for the "tiny" UC's.
http://forum.arduino.cc/index.php?topic=135623.0
There are examples out where such things as numeric pads and even old non-usb keyboards have been interfaced, but my belief is that Leonardo would be a better platform if cost were not an issue. Getting V-USB to work is straightforward, but the zeners and resistor values are critical components.
Ray
Officially, the arduino UNO has only a serial port that does not allow keyboard functionality to the device. However, this hack: Turning An Arduino Into A USB Keyboard | Hackaday makes it possible to do that using a firmware upgrade of UNO. This allows values of the USB HID tables to be sent over the serial port so that a keyboard or other usb device can be emulated.