How could pod2g have an untethered 4S and dev teams still haven't released tools to achieve this at home ?
The exploit I used to inject the untethering files to the 4S relies on having a developer account, and can't be released publicly. It's the same reason why @MuscleNerd has an iPad 2 tethered jailbreak but couldn't distribute it. So, we need to find a distributable exploit to remount the system partition read/write and to set Corona files at the correct places.
Why A4 version of Corona was easier to release ?
Because a tethered jailbreak is a good way to install Corona!
Why don't you do a tethered jailbreak then ?
A tethered jailbreak also relies on an exploitable vulnerability that we still haven't found yet !
Earlier this week, pod2g posted that he had made good progress on the jailbreak for A5 devices and said with some luck we could expect a release in a week.