The isotropic backend is written in Python. Python (though I love it very much) is about as slow as it gets. Attribute isotropic's scalability to implementer skill and not choice of programming language.
I admit that I have not used Python, however I have extensive experience with Perl (a similar interpreted language) and I can say that (surprisingly) it outperforms Java. I say surprisingly because Java is compiled into psedo-machine language which should theoretically be faster to execute than a purely interpreted language. I am not surprised that Python is more responsive than Java.
I think Isotropic is fast for a number of reasons:
1) Server is running Linux and not Windows
2) Web server is Apache and not bloated IIS or some big Java servlet engine
3) Python implementation is well-done
4) Interface (including Javascript) is simple and not bloated
5) Chrome makes it especially fast
I suspect that the commercial app will not be as efficient, however it may be possible for them to throw money at the problem to increase performance (more hardware, etc).