Sure, it might not be particularly useful or usable, but that doesn't mean it isn't totally cool. The screen is rather small, and I guess the mouse is being controlled by the five way pointer of the phone, but the phone itself is powerful enough to run Windows 3.1 easily, and I'm sure Windows 95 wouldn't be too much trouble either. DOSBox was used to emulate a 486-class processor.
The use of this? Well, fun, mostly, and a sense of "why not?". I'd love to be able to run Windows 3.1 on my Nokia E71; not because it would make any sense, but just because it's cool. With phones getting ever more powerful, there's enough spare cycles in there to dedicate to silly things like this.
If anyone can read Polish feel free to fill us in on the details.