There is a mouse and cat game going on between the Apple and the people working on jailbreaks for iOS 4. Recently a web-based jail breaking tool by JailBreakMe.com exploited the PDF vulnerability of the iOS and allowed the iPhone 4 and iPod touch users to Jailbreak their device. Apple had issued a fix to stop this jail breaking tool and also blocked this website in their stores. According to the JailBreakMe.com developers their code is open source and any one can further use/host it with GNU terms and conditions. Today apple have announced the that iOS 4.1 will be available after one week. At the same time there are some rumours around that the JailBreakMe.com developers are working to upgrade their code to jailbreak iOS 4.1.
iDevices with 4.1 (like iPhone 3G which does not rely on a carrier unlock, and iPod touch 2G ) can be jail broken using Redsn0w 0.9.5b5-5.