Hi,
SurveyPro has continued to be actively developed by Danielle Cordella and the current version is hosted at:
https://github.com/kordan/moodle-mod_surveypro
I have just downloaded it into a Moodle 3.4dev (Build: 20171006) local server and it works beautifully, in the standard Boost theme.
No errors reported with full developer debugging enabled.
There is some Moodle Docs information at https://docs.moodle.org/33/en/Surveypro_module.
I would suggest you to try it in a local server and, if it meets your needs, later proceed to install it in a real server.