No, it's fully open - it boots by default to the core CE desktop.
(It was the V110 and V150 that were closed.
)
I think the CE 6.0 dump-and-upgrade was just speculation - you can't just load a ROM dump; it's not the same format as a flashable ROM image. And even if someone has figured out how to convert a dumped ROM into a flashable image, you can't flash just any CE 6 ROM image - it has to be compatible with the device's hardware and bootloader. Put simply, it has to be a ROM image supplied by the OEM. You can't even flash the V212's CE 5 ROM image onto the CE 4.2 .net V210 - that we've definitely had discussion here about.