In the vast majority of cases this is simply a technique to protect the spammy links they stick in the footer. The problem is, as I said in the post, this could be used for something far more nefarious. Best course of action is simply don't use these themes.

The WordPress theme repository contains thousands of clean themes to choose from. Additionally, there are many reputable authors in the WP community who create wonderful themes. A few names that come to mind are Brian Gardner, Cory Miller, Nathan Rice, Darren Hoyt, Justin Tadlock, Derek Punsalan, Adii Rockstar. There are many more, these are merely a few of my favourites.

The vast majority of authors are reputable people but for whatever reason users keep downloading themes from shady sites. I don't know why this is. I'm thinking maybe its because these users are new and don't know where to get themes so they start Googling around and end up on shady site.

Yeah that curl bit was a new one for me to. That's the first time I had ever seen it used that way. I wonder how long that tactic has been used before I became aware of it.

That curl thing is particularly bad. People who are non-the-wiser could use that, leaving themselves wide open. If the curled site was compromised that potentially compromises all the theme downloaders. sigh.