You get a one time activation code for the "essential" version.
You can compare the versions here:
http://www.dxo.com/us/photography/photo-software/dxo-opticspro/editions
One of the main differences is the "Prime" denoiser for raw. It's a pretty powerful noise reduction tool, but you could pass through the output to Neat Image, if you have that already.
Also note about existence of http://www.picturecode.com/index.php
It is barebones converter (but pretty fast and useful for real work), it has NeatImage noise reduction competitor (in early days) - NoiseNinja inside.
Still works
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