Teemu,
I'm doubtful in any jurisdiction or with any program, would screenshots be considered subject to copyright. The screen representation of any program is not the "work". Particularly if you are using the screenshot to describe the program in a book or to present say the finding of your analysis, it would just be considered as "fair use." It would be a different matter if you were saying copying the look-and-feel or a critical design to another program. In that case you might be infringing on a design rather than copyright,
Of course I am not a lawyer, Martin