Tom.
Screenshots are considered to be "derivative works" under US Copyright
Law (refer to the US Copyright Act of 1976, Section 101 if you want
details). There is nothing wrong with including screenshots (as part
of your documentation) of an application running under Windows, OSX,
or any other operating system.
We are NOT fearful of the community, we want to RESPECT the
contributions of the community.
You are the only one who is saying anything about court cases and
lawyers, and imagining someone attacking LibreOffice.
What we are concerned with is respecting the rights and contributions
of everyone who has participated in the LibreOffice and Apache Open
Office (previously OpernOffice.org) documentation. That's it...
nothing more. The ambiguity of the license attached to the existing
Apache Open Office documentation is a minor issue that can
(reasonably) be managed... and to be honest I consider this issue
resolved and closed.
Anything more about lawyers and such silliness is bike-shedding
http://en.wikipedia.org/wiki/Bikeshedding
Clayton