Distribution

[Stefano Burchielli]

Hallo, my name is Stefano
i have 2 simple questions:
1)    I'd like to know which is the best distribution for use with GRASS.
2)    I've found some pages about integrations between GRASS and modeling
programs (water quality and quantity, groundwater modeling), but i couldn't
find any reference to available code (not only free byt also to be paied):
is it available?
Thanks a lot

SB