Sure, I just scared you with Group: Linux Potentially Infringes 283 Patents an hour or so ago, but now comes this: " First, Ravicher says, individual open source software users don't need to worry. The most a company like Microsoft could get out of them would be the value of products they didn't buy because they were, instead, using products that infringed Microsoft patents, and it simply wouldn't be worth Microsoft's time and effort to track all the users down and sue us.
Second -- and this is the big one -- Ravicher says the oft-quoted figure that only one half of one percent of all patents are overturned in court is misleading; that there are 200,000 patents issued every year, and only about 2000 of them -- that's one percent -- are challenged. And of those 2000 cases, the patents' challengers win 46 percent of the time. In other words, the win rate on legal patent challenges is closer to 50 percent than to one half of one percent. Seen in this light, a proprietary software company bringing an infringement lawsuit against an open source project isn't in a situation where it has nothing to lose and everything to gain, but has a nearly fifty-fifty chance of having its patent overturned. This figure makes it unlikely that even the most rapacious proprietary software company is going to start suing open source projects. No sane Board of Directors would want to take the chance of losing potentially valuable patents because of an attempt to pry money from people who probably don't have enough to make winning worth the risk."