Zombology is a free print-and-play card game from Eurydice games. It’s advertised as a 10 minute, semi-coop, card drafting game for 3 – 8 players.
CMON games offers a print and play version of its Xenoshyft game. The game combines deck building , resource management and base defense mechanisms.
Space Station Zemo originally was published in Inquest magazine in 1998. It’s very hard to find a secondhand copy these days, so a helpful gamer scanned the game and posted it it for people to read, and perhaps recreate for personal use.
Clash On The Fringe is a set of pay-what-you-want rules for military space adventure. They’re designed for use with whatever figures you have.
Unbound: Endless War is a free print and play game for two p layers in which you build a map and attempt to take over a players’ bases. It’s a pay-what-you-like game.