I know people still running Windows 98, 95, ME, and 2000. So people running Mac OS 9, 8.5, 8.1, or 7.5 doesn't surprise me either.
Intel i7 4790k @ stock, Asus Z97-PRO(Wi-Fi ac), 2x8GB Crucial DDR3 1600MHz, EVGA GTX 760
Samsung 950 Pro 512GB + 2TB Western Digital Black
Dell 2408WFP and Dell 2407WFP-HC for dual-24" goodness
Windows 10 64-bit