So this is a minor update, which fixing only the accuracy of the 3GS battery meter and the stability of some third-party app launches. This update is avaliable via iTunes.
New firmware 3.1.3 also introduces a new version of the baseband, the 05.12.01. So if you need unlock do not update! DevTeam also warns us:
If you care about your jailbreak and unlock, don’t update your device – 3G and 3G(S) owners should pay particular attention to this warning.
PwnageTool and redsn0w are not yet compatible with 3.1.3
Experimenters show that the latest version of redsn0w 0.9.2 is able to jailbreak iPhone 2G, iPhone 3G and iPod touch 1G. Just point it at the 3.1.2 IPSW (download here) after doing update or restore to firmware 3.1.3. Sounds like DevTeam will release an updated version of redsn0w that will handle firmware 3.1.3 officially. They say iPod touch 2G with firmware 3.1.3 is also jailbreakable.
Users report that unlock software, blacksn0w and ultrasn0w, doesn;t work with the new baseband.
Geohot, the creator of purplera1n, has just released his own iPhone 3GS softwareunlock and named it purplesn0w. Who is purplesn0w for? If you own a jailbroken iPhone 3GS running firmware 3.0 and you want to unlock it to use it with another carrier (T-Mobile only in the USA), then purplesn0w is for you. Are you experiencing wifi/battery/other unlocking problems after using ultrasn0w? Then I highly recommend you try purplesn0w. Geohot says that it’s the best unlock out there.
purplesn0w doesn’t run any deamon (resident app) on the iPhone, it just patches three files: CommCenter, lockdownd, and wildcard. You need an activated device in order to use purplesn0w, this is a minus.
Here is how to install purplesn0w:
Make sure you have an activated iPhone 3GS. If you have T-Mobile make sure you disable 3G in the settings.
Open Cydia, and add http://apt.geohot.com to your sources
Install the com.geohot.purplesn0w package
Watch for the success output in Cydia
Reboot your iPhone 3GS
Once you have followed the steps above, your iPhone 3GS should be unlocked.
Update: Geohot has also posted technical details of purplesn0w here along with the source code of purplesn0w. He plans to release an updated version of purplesn0w with hactivation support.