Hands-down the biggest dissapointment of the Motorola DROID RAZR launch announcement was the fact that despite Moto's commitment to more open bootloaders, the flagship phone would be locked down just like previous Motorola-Verizon devices. Even after considerable customer backlash and unlocking the bootloader on the international GSM RAZR, not to mention the fact that both Samsung and HTC have provided unlocked bootloaders for their own Verizon phones, Motorola has stood frustratingly firm. Now a pair of modders have found away around the locked bootloader, opening up the possibility for true custom ROMs.
The mod comes from Eternity Project forum users "kholk" and "[mbm]" using what's known as a kernel execution or "kexec". This loads up a secondary kernel directly into a device's memory, running on top of the original "locked" kernel. This is significant because it will allow users to run custom kernels instead of relying on the latest kernels delivered by Motorola and Verizon. While custom ROMs and recoveries are possible on devices without an unlocked bootloader, they're always something of a hack job, and must rely on older kernels. This usually means that ROMs of newer operating systems, e.g. Ice Cream Sandwich, are severely limited in their utility, stability and performance.
Not that the current project is perfect. After the custom kernel is executed, only one of the DROID RAZR's 2 CPU cores will work, and some phones just seem to reject the mod entirely. This is probably due to some component being supplied by two or more OEMs, but there's no way to be sure. The installation is easy, assuming you've already got some kind of custom recovery installed, but you may want to wait until the kinks are worked out before trying this solution. It carries a higher than normal chance to brick your DROID RAZR. On the plus side, waiting a few weeks for a more complete version should allow ROM devs to gets some fancy new versions of Android ready for the DROID RAZR and DROID RAZR MAXX.