Wrong. The GPL is relevant as long as lawyers exist to make a
quick buck out of FUD.
Yes. The problem is not always what the authors intend as
restrictions, but rather how your company's lawyers interpret
the wording in their license. In practice, I'm sure that you'll
never have the slightest legal problems using g++ for
development, but corporate lawyers often have problems getting
their heads around the idea that the authors of the license
might actually be honest people, and are not out to trick you
somehow.
And FUD is still - unfortunately - a relevant factor in
business decisions. Because if you want to sell your software,
you cannot afford to doubt whether it would be legal.
There's no doubt in my mind. But then, I understand a little
bit about how such software is developed. It can be difficult
to convince white collar management that the FUD is just that,
FUD.
For example, I note that you do not mention linking in GPL'd
libraries.
Don't do that, or you do "contaminate" your product. That's why
gcc's librarys are LGPL, and not GPL---so that you can link
against them without contamination.
At one time, there was a problem concerning templates, inline
functions and even #define's; the LGPL didn't really make clear
that this wasn't contamination. Presumably, a few #defines
would have been covered under the "fair use" rules, or something
like that, but it was a problem with templates in C++---many
librarys are only header files (so you are, in fact,
incorporating source code into your application, and not just
linking against a library). I'm fairly sure that this was never
the intent of the authors of the C++ standard library, but it
wasn't really clear in the wording of the LGPL. I think that
the libstdc++ comes with an ammended LGPL now, however, which
explicitly says that including a header counts the same as
linking against the library, and thus doesn't contaminate
anything.
With regards to libraries in general: make sure that they are
LGPL, and not just GPL, and don't modify them in any way, and
you should have no problems. (In general, for any third party
libraries, LGPL'ed or commercial, it's probably best to keep the
library is a separate, write protected directory tree, on its
own.)