“Cisco was essentially compelled by the threat of legal action to release the Linux-based firmware under the GPL, but it was not thrilled to see that the device whose success finally gave it the foothold in the home that had long evaded the company being used in ways beyond what the box said.”
A supplier slipped Linux into the WRT54G firmware and nobody at Linksys noticed. The GPL forced Cisco to publish the code, and a whole generation of custom router firmware grew out of it. Cisco never wanted any of it. The best thing it ever shipped was an accident the license made it share.