Dell used the CAF 8260 GB sources when building 4xx roms, they simply backported whatever they need to from their already working 3xx codebase for whatever was needed (i assume)
CAF itself dropped support for 8x50 in their GB codebases, but the 8x60 is close enough it didnt really matter ultimately.
Much of the drivers arnt even in the kernel, they're in the android userland which is Apache and not gpl, hence the driver issue.
Which ever method you (presumedly do) to get the kernel booting under ICS doesnt really matter, but the more difficult/time-consuming methods will ultimately be more useful for porting to newer kern versions.
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