It’s still not clear exactly what happened to NetShare; the makers of the program told posters on the MacRumors forum that they haven’t heard a peep from Apple.

But it seems obvious that Cupertino pulled the app off iTunes shortly after it went live—and probably at the behest of AT&T.

AT&T doesn’t allow iPhone users to tether their laptops to the phone’s data connection, although several overseas carriers offer “phone as modem” plans for the iPhone 3G. Indeed, laptop tethering is a common feature for most 3G smartphones.

I didn’t get a chance to test NetShare before Apple pulled it from the App Store, but according to MacRumors, the program lets you connect your laptop to the iPhone via the handset’s Wi-Fi connection. The process involves configuring your iPhone’s IP address, enabling the SOCKS5 proxy option on your Mac or PC, and then entering your iPhone’s IP into the proxy server field. (Click here for screenshots.)

NetShare works on either the iPhone 3G or the original iPhone with EDGE, and users reported that the program works just fine, MacRumors said.

A post on the MacRumors forum that bills itself as an “official reply from Nullriver reads, in part:

We’re not quite sure why Apple took down the application yet, we’ve received no communication from Apple thus far. NetShare did not violate any of the Developer or App Store agreements. We’re hoping we’ll get some feedback from Apple tomorrow. Sorry to all the folks that couldn’t get it in time. We’ll do our best to try to get the application back onto the App Store if at all possible.

Well, Nullriver may not have violated any developer or App Store agreements, but check out this clause in AT&T’s terms of service:

[P]lans (unless specifically designated for tethering usage) cannot be used for any applications that tether the device (through use of, including without limitation, connection kits, other phone/PDA-to computer accessories, Bluetooth® or any other wireless technology) to Personal Computers (including without limitation, laptops), or other equipment for any purpose.

That’s pretty much the ball game, unfortunately. Still, you’ve got to wonder—why won’t AT&T offer an official tethering plan for the iPhone 3G?

Update: MacRumors reports that NetShare is back on the App Store, but only via direct link. Also, be aware that you run the risk of violating AT&T’s TOS by using NetShare, not to mention running afoul of any data usage caps.

Share your iPhone’s EDGE or 3G Internet connection with your computer using NetShare. NetShare provides a SOCKS5 proxy for your computer to connect to.

NetShare’s inclusion in the App Store is a curiosity, as Apple must have manually approved its inclusion. It’s unclear if the Application would go against AT&T user agreements. AT&T typically charges Smart Phone users $30/month extra to use tethering applications. Screenshots of the application’s instructions have been included here:

This application has been confirmed to work by multiple users. NetShare is available on the iTunes App Store.