It's probably fake. (At most, it
may jailbreak 4.1, but just the iPhone 3G and "MB model" iPod touch 2G since those have been "pwned for life.")
For everybody waiting for the 4.1 jailbreak, keep an eye on
Chronic Dev and the
iPhone Dev Team (but do NOT harass them for a release; a jailbreak will be released when one is ready!). Chronic Dev has a bootrom exploit under wraps that affects the A4 devices, and may affect "new bootrom" models (new iPhone 3GS units, "MC model" iPod touch 2G, iPod touch 3G).