Besides Megagun and Shadowlord (and of course Alex!), the following people have contributed code or other tools/files:
Bensel	(Hopper highlighting code)
The Reflection	(Exponential atmospheric pressure)
Ees33 (New surface algorithm and surface fixes, which are currently disabled but in the source still)
MopedSlug - USERS MANUAL
Stargazer - Additions to USERS MANUAL
Ireclan - Additions to USERS MANUAL
Ryan J. Bury - I think he's got some stuff inside the USERS MANUAL, too..
Mvgulik - Help.com module

