I'm writing some PDF for a commercial company. I use XeLaTeX to produce the PDF. Currently they ask me to change to MS Word because they have buy the licence. Does the LaTeX have commercial limitations on the produced PDF? Or is there any licence required to use LaTeX?
(La)TeX is free to use, but with some restrictions (not copylefted is probably meaningless in your case). You can see the licence for example here: http://www.latex-project.org/lppl.txt. Information about licence of XeLaTeX you can find even here: http://en.wikipedia.org/wiki/MIT_License (I know: Wikipedia is not a perfect source).