phpVMS v3 has not officially been released yet and there hasn't been an update on the github repo. in over 4 months, so it's currently on hold.
That version there is probably an unfinished version which is not meant to be run yet. If you are looking to install phpVMS at the current time, try this one
https://github.com/DavidJClark/phpvms_5.5.x
When phpVMS v3 gets released (or gets an official update), I have no idea, but I guess we wait.