Simple question

[Byron Blue]

We are considering moving our operating system to the Linux environment.
Our product is a commercial OMNI sonar system used throughout the world in 
the commercial fishing industry. The software itself and upgrades are free 
of charge to the user.
Of course, my choice for the compiler would be GCC.
I should initially point out that I am unfamiliar with both Linux and 
therefore GCC.

This is the question:
  GCC uses the GNU license scheme. This operating system would be embedding 
in our industrial computers and I do not (of course) want the source code 
for our operating system to be open source - available to our competitors. 
The GNU site is not quite clear in this area and being new I would not want 
to "break the rules". Could I ask you for a bit of clarification on this 
issue?
Thank you for your time and efforts,

Byron Blue
Software Engineering
MAQ Sonar