As usual, A4 idevice or older idevices still can be jailboken no matter what iOS is, and same with the latest iOS 6.1 beta 4 for developers, who can also enjoy a tethered jailbreak on iOS 6.1 beta 4 thanks to the always reliable Redsn0w, If you are the one of these developers, please head to the step-to step guide:

How To: Jailbreak iOS 6.1 Beta 2 Build 10B5105c On iPhone 4, iPhone 3GS, iPod Touch 4G With RedSn0w 0.9.15b3 [Windows]