iPhonelinux is not actually a hack/exploit neither an unlock, but it is based on the Pwnage exploit.
There are three steps in the iPhonelinux roadmap : oPeniBoot, linux kernel and long term (GUI, phone...)
The Goals of OpeniBoot is to run low-level code, to have low and critical drivers (nand and nor driver, NVRAM...), debugger and developpement environment (chainloading, upgrading itself and USB mass storage).
A linux Bootloader, a working linux kernel (just a question of cross-compiler), porting drivers, run wifi and command line thru SSH.
Multi-touch driver, Baseband driver, port X server and create an SDK. Then have a viable alternative of the iPhone OS.