GRASS 6: The manual has been integrated into the source code (doxygen format) and can be extracted with 'make pdfdocs' or downloaded from this page.
Contents of directory lib/:
bitmap : bitmap library for X Window Bitmaps
btree : binary tree library
bwidget : tcl/tk extra library
cdhc : library for testing normality and exponentiality
D : display library
datetime : DateTime library
db : database management interface database drivers + SQL parser (DBMI)
display : library for CELL driver
dspf : G3D display files library
edit : edit library
external : external libraries from other projects (shapelib)
fonts : Hershey fonts
form : forms library
front.end : interface for interactive modules
g3d : G3D raster volume library
gis : main GRASS library
gmath : generic mathematical functions (matrix, fft etc.)
(later to be extended, BLAS/LAPACK library)
gtcltk : Tcl/Tk stuff
image : extra imagery library (image3)
imagery : imagery library
init : GRASS initialization code + scripts
linkm : linked list memory manager
ogsf : openGL (R) library (required for NVIZ)
proj : PROJ4.4.x projection library
raster : GRASS raster display library (raster map functions are in gis/)
rowio : row in/out library
rst : library for interpolation with regularized splines with tension
segment : segment library
sites : old Sites library, now interfaced to vect library
symbol : drawing symbols for point vector data
vask : curses management library
vect : GRASS vector and Direct Graph library