Consider a service such as Netflix... if on the server side netflix used code with a GPL license attached, do they have to make their server side code available under the terms of the GPL.

Obviously netflix being only an example, the company I worked for mostly provides 'services', we don't sell software that anyone can download to their computers, more like, computers over a network talk to our computers and stuff gets done.

Can I consider using GPL code in this environment without making all my code 'open source'?