Wirelessly posted

There is no chance of JL_CMDER itself damaging your blackberry, but the whole operation is not without risk. You will wipe the OS from the device and be left with the 507 error (no operating system). You will then install an OS. If you are comfortable doing that (and sounds like you are), then you'll be ok. Just use a reliable computer and don't do something like let a laptop battery die or windows crash in the middle of the operation.