Note that it's OK to *accidentally* implement patented algorithms as long as the author of the contribution didn't know about. There's no trebble damages in that case, and no tainting of others, plus, contributors and code reviewers/committers can't be expected to do patent searches for each contribution.
Non-lawyer here, but "OK" is not a description I would apply to implementing a patented algorithm. You might be thinking of copyright. Of course it is true that people can't reasonably be expected to do patent searches, as you describe, but the patent system as applied to software is not well-known among knowledgeable people for being reasonable.
