Kladdehelvete
Is it true that the A+ pathfinding algoritm is patented?
The original paper on A* search was published in 1968, almost 50 years ago, and the authors of that paper did not hold a patent. So no, there is no valid patent on A* search itself.
But remember, we're just recovering from a crazy period in US patent history. It's possible that someone was granted a low-quality patent on some alleged "invention" which involves A* search somewhere who may try to assert said patent against you. Given how ubiquitous A* is, however, it doesn't seem like a huge concern.