I just answered this question on the mailing list query, but I am posting a copy of the solution here as well:
The problem is that the proper command to run is "pbi_makeport" not "pbi_portmake".
If you just copy and paste the full command that EasyPBI generates and displays on the CLI, it will avoid errors like this in the future.
As an aside: the new version of EasyPBI is actually included with the upcoming PC-BSD 9.1, and builds PBI's without needing this workaround anymore. If you switch over to the current PC-BSD 9.1-Beta1 image, you can start using it immediately.
~ Ken Moore ~