Commercial Development

[Robert Dewar]

Most certainly you can use the gcc compiler to compile commercial applications.
Indeed many free software programs are sold commercially, including gcc itself.

Now if you are asking whether the license restrictions you plan to use for
some proprietary software are compatible with use of software with other
licenses (e.g. GPL, LGPL, ...) you are asking a legal question. You need to
get proper legal advice on this question. Not only is it illegal for 
non-lawyers to give legal advice, but in any case asking for legal advice
on a list like this is unlikely to provide any definitive answers or answers
that you can rely on.