Chris has YC funding now, so surely he doesn't need another 7k from the Internet to make sure Python support is in.
In general, regardless of how much funding one might have, one would also like to have the maximum dollar value of sales possible. Kickstarter facilitates this both by enabling sales-like revenue in the first place, and by enabling price discrimination. I'd need to learn more about the Kickstarter funding mechanism to understand whether the sales analogy is totally appropriate or just partially so, but it seems to me to be the far better analogy when compared to venture funding.
Edit: And I think the point stands notwithstanding the fact that Light Table won't be free software.
All I'm saying is that it's not like he's going to run out of money to build in Python support.