LightZone for Linux. It's free for *nixes.
The Gimp with DCRAW and UFRAW (which installs the Gimp plug-in for DCRAW) can read almost any RAW format, even DNG. UFRAW comes as a stand alone version with a nice GUI. Very fast and reliable, but you should read the DCRAW options before you use UFRAW or open a RAW in the Gimp with the plug-in.
It is free (as in no money changes hands), and may be a useful program for someone running MS Windows of some sort, but it's not open source, which implies greater freedom(s). Open source means you can download the source code, modify it for your own purposes, redistribute, etc.
No axe to grind, just clarifying terms. Photoscape might more accurately be described as "freeware".
Along the same lines, recent releases of LightZone for Linux have been changed to expire after a certain date, and it isn't really open source either, for the same reasons as Photoscape.
No need to apologize to anyone, especially me. 99% of computer users are unaware of the importance of the philosophy behind open source, which is the only real challenge to monopolistic software giants dictating what we can and can't do with our computers. And to be clear, not being open source doesn't make Photoscape "bad" as far as I'm concerned.
Actually, Photoscape is more "free" than Lightzone. I looked at downloading the new Linux version of Lightzone yesterday and it was hardwired to expire in 3 days, not worth the download time.