Most software developers agree that software patents are hopelessly broad and that violation is almost unavoidable for any non-trivial software project. I won't even go into examples of software patents causing industry chaos — new high-profile patent attacks appear every month. The risk of software patents to the software industry has been likened to a mine field, and for good reason — it is impossible to guess when software patents will create a crisis.
The Postgres team has been circumspect about software patents — we address them when someone brings up a possible violation (as happened in 2005 with a patent on queues), and we try to avoid patented ideas in our code, as you can see from our recent discussion about compression algorithms. Several years ago, one of the Postgres support companies analyzed our source code for possible patent violations, and reported we were clean, but given the "mine field" unpredictability of patents, it is hard to trust the report's accuracy.