Earth is out of resources. Humanity's population continues to grow. Join Frontier Systems and explore the galaxy, looking for new systems and new planets to help our species survive. Will you work with others or on your own? Will you fight or explore and colonize? The choice is yours.

Frontier is an addon for Garry's Mod that brings spacebuild back to its roots, and adds some new features. Enjoy new visuals, stay alive within a space suit, and colonize other worlds.

Unofficial thread with info:
http://www.facepunch.com/showthread.php?t=946049

Credits:

Coders
Chad 'Jinto'
Jeff 'TheJ89'
Brian 'Shanjaq'

Modelers
Andrey 'Lazermaniac'
Garret 'Slash'

Mapper
John 'DaApocalypse'

Music and Sound
Jon "Moose" Tetrino
IceTec