Fractured Space is an Early Access Game! And as stated in the Early Access Game box on the Steam store page, it will eventually transition to a Free to Play model upon official release. So the developers are just giving more people a chance to get into early access without having to buy a founder pack (normally $9.99).
There are also some extra bonus. Developer Edge Case will offer every existing player, as well as any new players picked up during the weekend the following in-game rewards in future updates:
Exclusive captain based on Fractured Space YouTuber The Mighty Jingles
New standard skins for each of the three starter ships
Exclusive community-voted legendary skin for a TDS ship, much like the Goliath, this will incorporate a unique silhouette and VFX for the craft.
The exclusive legendary skin gets upgraded to an exclusive TDS premium ship
Play Fractured Space until Monday April 20th at 10AM Pacific Time and keep the game for free!