To quote the IndieGoGo:
"If the goal is not reached, don't worry; the game will still be finished, it
will still be completely libre software under the GNU GPL, and you will still
get your perks. I just won't necessarily publish ReTux to everyone at no cost
as described in the previous paragraph (I might charge for copies instead,
for example), and may take a bit longer to finish the game."
If the funding goal isn't reached, onpon will distribute the game and source
code to people that buy the game after and during the funding.