The gdefaults2 file is usually located inside the .crossfire directory.
This file applies to the new gtk-2 client for crossfire,
The older gtk-1 client used the gdefaults file as configuration file.

At the top of the file one reads :

# crossfire-client-gtk2 automatically generates this file.
# Manual editing is allowed, but the client may be a bit
# finicky about the keys and values.  Comparisons are case
# sensitive.  'True' and 'False' are the proper case, but
# have been replaced with 1 and 0 respectively.

Where the part 'True' and 'False' are the proper case
once applied to the X11 cfclient configuration file defaults .

The code in function load_defaults() in file client/gtk-v2/src/config.c parses as follows :

        if (inbuf[0]=='#') continue;
        /* Skip any setting line that does not contain a colon character */
        if (!(cp=strchr(inbuf,':'))) continue;
        *cp='\0';
        cp+=2;      /* colon, space, then value */
 
        val = -1;
        if (isdigit(*cp)) val=atoi(cp);
        else if (!strcmp(cp,"True")) val = TRUE;
        else if (!strcmp(cp,"False")) val = FALSE;

Meaning, that lines starting with # are ignored,
lines need to contain a colon : or are ignored,
and may have any content, but digits *not* -1 ,
and still recognizes True or False in case sensitive string comparison.

See the gdefaults configfile, since the gdefaults2 does not differ much.