For open-source Alpha emulation, there is AXPbox, which is a fork of the somewhat ancient es40, with some new fixes. It even runs on m1 macs now.
DEC would have been profoundly wise if they had recognized and adopted ARM, porting VMS to it.
Maybe Cutler would have stayed in that early fait-accomplis. They also never would have spent the money on Alpha, or wasted time selling MIPS workstations.
There are probably free Alpha emulators by now, but the VAX version has been running on PCs for a long, long time, and it's what people know.
http://simh.trailing-edge.com/