A single Kickstarter pledge for Firmament (at the $30 or higher tier) entitles a backer to one copy of the game. 

Kickstarter's rule is: A single pledge to a project provides a single copy of whatever rewards the Backer's pledged tier offers. Multiple copies via a Kickstarter can only be obtained by making multiple pledges, and due to Kickstarter's framework each individual separate pledge to a single project must be made using a different Kickstarter account.  

The PC/PCVR/Mac versions are scheduled to launch on May 18th, 2023.

If you made a single pledge to support Firmament on either Kickstarter or Fangamer, or if you're waiting to buy the game when it launches, you can purchase additional copies when the platform you want to play on is available, on or after May 18th, 2023.