Determining if this module is needed for Drupal 8.
Contact Storage( +Core Contact)
This module adds much of Drupal 7 EntityForm functionality to the core Contact module. Many of it's features are likely going to be moved into Drupal Core.
There is a roadmap issue for getting features into Drupal core:
Phase 1 of the roadmap has been done. Phase 2 has an issue to get approval:
Contact Storage has over 4500 installs(rising fast) and is at 8.x-1.0-beta7.
This module does not use the Field API. It has form creation user experience that is more similar to Webform than Entityform or Contact Storage.
YAML Form has over 2000 installs(rising fast too) and is at 8.x-1.0-beta19.
Is this module needed?
Given the 2 options above is this module still needed? Would it make more sense to join force with Contact Storage?
Developing this module well would be a substantial, ongoing commitment. I, as the maintainer, don't have the time for this.
I would be willing to help facilitate further development continue if it is determined that it is still needed considering the 2 options above.