What a bad luck! Read on.. :)
A chip company had an Ethernet controller chip, and they engaged outsourcers in a Far East country to develop some software drivers for it. They sold the chip, together with the software drivers of course, to a company called Linksys, which incorporated it into the design of their four-port router. It was one of the most popular of the smaller routers. In the process of doing this, Linksys added their own code around these software drivers and then they marketed the unit. It just so happens that the outsourcer the chip company had employed at some point inserted a piece of code subject to a GNU General Public License, or GNU GPL.
One of the properties of the GPL license is that you can use it and you don't have to pay anything, but any code that's written around this piece of code, and any modifications or derivations of the code, also become GPL. That means that you have to make the code publicly available. You basically must open up your code. Now Linksys probably wasn't aware that they had such code. Then, of course, Cisco acquired Linksys and inherited the technology and the router and the code. Cisco then began using the code in other sections of their own products. So, suddenly, a whole bunch of products at Cisco are now 'contaminated' with GPL code, which means that Cisco is in the unenviable position of having to 'open up' their valuable proprietary code to the public.