Limera1n and GreenPois0n: Let's Clean Out What's Going on!
For people wondering about the difference between iBoot and bootrom exploits, Geohot found this vulnerability a while ago when both iBoot and bootrom contained the code that made them vulnerable. Apple noticed that iBoot contained a bad code so they fixed it in iBoot not in bootrom. Geohot noticed that Apple will fix bootrom exploit in the next generation devices by full hardware revision so he made the right decision by releasing Limera1n tool before Chornic Dev Team. Just to save SHAtter exploit for 5th-generation devices as iPhone 5 or iPad 2.
You may say, "Why didn't Geohot save his exploit for 5th-generation devices?". Well, Geohot's exploit works on all devices not as SHAtter which works on A4 devices only, so it was better to release Limera1n and save SHAtter.
Now, GreenPois0n & Limera1n tools are both based on the same exploit, so there's not any difference in both the tools, don't ask me which is better? I prefer using Limera1n but in case you faced some errors so go ahead and try GreenPois0n.
For people asking about Mac OS X version of both tools, there will be a Mac version of GreenPois0n but not in Limera1n as Geohot's site claims it will be available in 7 years (blah!). Also, iPhone Dev Team is working on PwnageTool for Mac OS X coming out this Sunday (as usual) and will support Apple TV.
Unlock? No, there's no unlock yet for baseband 05.14 and 02.10 and will not be before iOS 4.2 final release which is scheduled early in November. Hackers as Sherif Hashim has mostly finished the hard steps and MuscleNerd confirmed that ultrasn0w update will be available after iOS 4.2 release. So, for all iPhone 3GS, 3G unlockers, stay away from upgrading to iOS 4.2 (iPhone 4, use this guide) or you will not be able to unlock except after at least one month.