Why does the shirt have an obfuscated bash script on the back?

Because it's by Akamai, the blog links to https://www.akamai.com/newsroom/press-release/uniqlo-adds-ne...

Uniqlo frequently does collaborations. This was one with a tech company

It's at least the second one that Akamai's done, although I like this newest one the most.

The old one was: https://www.uniqlo.com/us/en/products/E459561-000/00

I have both of them and wear them to work regularly xD

The guy who founded the new political party Team Mirai also wears it frequently: https://en.wikipedia.org/wiki/Takahiro_Anno