p0f v3 is a passive operating system detector. The latest release is 3.08b, dating to November, 2014. Given the releases of Windows 10, multiple Linux, Firefox and Chrome versions since then, the fingerprints file doesn't identify a lot of TCP SYN packets all that accurately.
I found a p0f v2 fingerprints file that used to be maintained by CMU's Software Engineering Institute, but I can't find any v3 fingerprint files. Do other people/organizations produce updated fingerprints files for p0f v3?