Originally Posted by Mrs Beanbag
Not necessarily, it depends on the license. LGPL, for instance, is designed to explicitly allow commercial use.
And it isn't true of GPL either. GPL isn't a good licence for hardware as it is hard to distinguish if other parts of a system is an extension of the GPL part or if it is separate and just communicating with the GPL part. Not strange as the GPL is intended for software.
Most licences aren't viral in any definition of the term - BSD, Apache etc.