> Or you require the packages to have the GPL. That way changes can be
> made when needed by those who need them.

have a look at latex/1600 (a number I still have burned in to my brain
all these years later:-)

GPL is a good model for an implementation, but a very poor model for
something that is defining a user level language (as is a package,
usually) a GPL'ed longtable.sty would allow anyone to issue an
`improved' that is to say, incompatible, longtable.sty at any time, with
the same name. So no documents would be portable, anywhere.