MD5 takes an arbitrary amount of input and yields a 16 byte hash. This RNG continually MD5's a 16 byte digest, and uses the bottom N bits as the random number yielded, where N is just large enough to include the largest random number desired, e.g.:
To yield a random number between 0 and r:
create mask which has enough bits to include all of r
(for example, if r is 100, mask would be 0x7F)
do {
digest = MD5(digest)
number = digest & mask
} while (number > r)
The digest should be loaded and saved to a disk file between invocations of a program using the RNG.
The random number generator is used by the dice server.