There are three versions of Irreco.
Irreco Widget is a simpler and more easy-to-use version of the full (Qt)Irreco application.
QtIrreco is made with Qt-library. For user it's supposed to be simpler and lighter version of Irreco. QtIrreco supports only one backend which is the internal IR LED in N900 device.
Irreco is a remote control application for Nokia N900 (or N8x0). With Irreco you can control IR compatible devices like televisions, DVD players and AV Receivers. Irreco also has a remote editor which you can use to place buttons to the screen and build the kind of remote you want to use.