A question about docbook stylesheet licensing

Hi!

   Reading the docbook FAQ entry on stylesheet licensing  
(http://www.dpawson.co.uk/docbook/reference.html#d17e1969) it is not  
entirely clear to me whether the license on the stylesheets is viral, i.e.  
can I distribute them with a commercial application without having to  
publish the sources for the said application? I tried reading the license  
(http://docbook.sourceforge.net/release/xsl/current/COPYING) but as IANAL,  
I’m not completely certain about whether this is a viral license or not.


       -Antti-