I think it would be nice if the linked kickstarter page (which has many "why this" and "what about that" answers) explained why they chose Python. I'm pretty baffled. Just because it's popular? Better to pick C# then. Because it's... er, I can't even think of another reason.
Let's consider the "obvious" choices by examing the TIOBE top 10:
1. C - Not really the target audience of a tool like this.
2. Java - See above, plus plenty of competition.
3. C++ - See C.
4. Objective-C - See C, also arguably a bit of a niche (iOS).
5. C# - See Java, VirtualStudio dominates.
6. PHP - Yeah, right.
7. (Visual) Basic - Who are you kidding?
8. Python - Oh, right.
9. Perl - Only ranks high because of sys admins.
10. JavaScript - Already covered.
11. Ruby - Like Python, see below.
Basically your question seems to boil down to either of these:
1. Why was Python picked over Java/C#?
2. Why was Python picked over Ruby?
As for #1: the answer should seem obvious if you consider the category the three languages (JS, Clojure and Python) share. Plus, the market is very different and the competition is very strong and established.
As for Ruby: It's probably personal preference. There really isn't any objective reason to pick Python over Ruby or vice versa. The two are more similar than either of them would like to admit and they are perfectly interchangeable in most situations.
