Will this be possible? If this was not text, but free software
released under the GPL, the entire book would be have to be
released under GPL. That's the "viral effect" of GPL, as intended
by its creator Richard Stallman (and hated by Microsoft). Is
there no such viral effect at all in GFDL?
Would there be any difference in this respect if Wikipedia had
used a Creative Commons Share-Alike license instead?
(I'm fully aware that CC didn't exist in 2001, when Wikipedia was
launched. I've been following this discussion since then. I'm
not yet aware of any case law or court cases where the
consequences of Wikipedia's GFDL status has been tried.)
Well you can use gpl software with non-gpl software.
In the case of this book, it would be easy to consider it as a
collaborative work where some parts are released under GNU/FDL while
the other parts are released under classical copyright (or any other
licence).