Can the unfulfilled legal obligations in open source really lead to lawsuits?
There have been a series of lawsuits related to unfulfilled legal obligations from open source licenses over the years. Verizon, for example, was sued by the Software Freedom Law Center on behalf of Busybox, which is a GPL licensed package.  The claim was that one of Verizon’s suppliers used a GPL licensed package in Verizon’s FIOS wireless routers, without fulfilling the re-distribution obligations of GPL. This claim was settled when the supplier agreed to provide its source code free to the public, appoint a open source compliance officer, and pay the plaintiff an undisclosed sum.
In recent years there have been similar claims against Cisco, Diebold, Monsoon Multimedia, Skype, High Gain Antennas, and Xterasys.   While a couple of these cases are still pending, most of these cases have been settled. 

For all of the cases that settled out of court, the settlement provisions were in favor of the plaintiff and were similar settlements to the Verizon case.
In the cases that were ruled on by the courts, the courts have ruled that the license obligations are enforceable, ie, the fact that no royalties exchanged hands does not make the open source license any less enforceable.  The courts have also ruled that companies that did purchased their commercial software from a third party but then distributed it to their customers, are still liable if the commercial software includes open source where the license obligations are not met.  Since these companies often have more financial resources, they represent an attractive target for these type of lawsuits.
Copyright Source Auditor 2008.  All rights reserved.