Seems it doesn't apply to windows 9x... so windows 10 ?
Yes, a transparent window covering the entire desktop works fine here on my Windows 10 laptop. Because of the opportunity for this to be misused to cause annoyance (or worse) I expect it can be disabled using a deployed Group Policy, so don't be surprised if it doesn't work on a 'corporate' PC.
Be aware, though, that it's not too unlikely that the desktop will be bigger than BB4W's maximum window size. So you may need to use the code listed under 'Using windows larger than 1920 x 1440 pixels' in the BB4W Help manual.
I have in the past had dinosaurs roaming around my desktop using this method, but Microsoft stopped shipping the dinosaur sprites with Windows a long time ago!