My memory is very foggy, but IIRC Id's releases of source tend to be a
dump of some old snapshot of their source made some time ago, and then
they'll slap a GPL file in the toplevel directory. The intent is to
relicense it, but it leads to some confusing trees. They may have not
put the GPL in the tarball for wolf3d at all, and only made a statement
aout the source's license or added a sepeate file to their FTP site.
Then again, I could be confusing their release of wold3d with that of
doom. Try going back in the archives and finding the release
announcement for wold3d.