How can I install rosetta in my computer?

Ok,

Let my explain you my weird case.

A friend shared with me a GBA emulator for Mac. I opened it and the next window appear:

I assume the VisualBoyAdvance doesn't detect my internet's signal because I have something like this:

So, I looked for some information at internet and well, there is a way to install "Rosetta" using the Snow Leopard's CD but my problem is that I am a mexican living in Japan, I left my CD in mexico! I didn't thought I will need it :/! How can I do to install rosetta?

P.S: I am not able to download ilegal things because here in Japan is very dangerous to do that kind of things :/! I need a "legal" way to do it hahahaha!! Sorry!