Ok, the wording on that site is a bit odd to me. The name plan9port is a project Russ Cox wrote, so the wording
A port of 9front's version of sam(1) to unix (plan9port)
seemed to imply porting 9front's sam(1) to plan9port. That didn't make sense to me since Russ's plan9port sam goes back many many years earlier than the 2014 timestamp in that repo you pointed at.
Jim