That's hugely broad. Basically they won't sue startups unless the startups sue them first.
I love this approach, but it should also be pointed out that this is a very easy approach for a patent-poor company to take. If you don't have many patents, you aren't going to sue other companies who do have patents and you'd sure like to look like the good guy if you infringe on their patents.
Actually, it appears to mean that they won't sue startups unless the startups sued _someone_ about a patent in the last 10 years, unless that suit also qualified as a Defensive suit, which means that the suit is against _another_ company that hasn't sued anyone about a patent in the last 10 years, unless _that_ suit was a Defensive action.
frankly i think the recursion is both deliberate and good--if it's written properly (i haven't reasoned through the fine points completely), it partitions the world into two groups: those who've never started a patent fight (against anyone), and those who have. members of the first group can't sue each other without being reclassified into the second group, at which point everyone left in the first group can sue them without being reclassified.
I love this approach, but it should also be pointed out that this is a very easy approach for a patent-poor company to take. If you don't have many patents, you aren't going to sue other companies who do have patents and you'd sure like to look like the good guy if you infringe on their patents.