Havent looked for CD check in single yet. The change above will not prevent FS2 from looking for a CD, but it will eliminate the "must have 1 CD for every 4 players" nag in multi.
Here's a simple fix to eliminate the CD check itself (multi only, I think):
In .\GlobalIncs\PSTypes.h find:
#if defined(MULTIPLAYER_BETA_BUILD) || defined(E3_BUILD) || defined(RELEASE_REAL)
#define GAME_CD_CHECK
#endif
Change to:
#if defined(MULTIPLAYER_BETA_BUILD) || defined(E3_BUILD) || defined(RELEASE_REAL)
// #define GAME_CD_CHECK
#endif
It might be cleaner to just remove all calls to the CD check routines, but sometimes it is just plain easier to do a 1-line sledgehammer fix. Note that this probably won't eliminate CD checking in single.
Edit:
Looks like this will remove all CD checking in single and multi. Please note that I have not tested this at all.