I recently tried Raw Therapee 3.0 (release).
It's a software designed according to the canonical principles of open source programs:
- it crashes on startup (on my Mac).
- there's a known (?) fix on a forum page, unreadable because of crucial typos (what is libycup anyway?) and in fact it won't work.
Anyway, the Windows version is fine (v2.41 instead used to crash consistently as soon as I opened the first photo) and if it starts, it does the job.
It's based on the linux principle "any single command or function shall have at least 512 fine-tuning parameters": 256 undocumented, 128 unknown, 64 deprecated, 32 use-at-own-risk and the remaining reserved (for backward or forward compatibility, but not for present compatibility, so installing the same binaries on two different machines, they will behave differently)
For example, you can choose the RAW (sorry, raw) demosaicing algorithm between 84 different (but are they really?), just in case your favorite closed-source Lightroom introduced nasty errors (which never happened to me in the last 5 years, but, hey, you never know).
Anyway, it's a very nice alternative, a last resort when everything else fails.
One more good point: the instruction manual is a 35-page pdf, which, if divided by the number of free parameters, may not seem much, but it's good for those who don't spend much time on the documentation and "just want things done" (but how?)