A practical free workflow on Mac will likely require multiple apps rather than one all-in-one program. Based on the answers, a workable approach is:

• use an organizer/uploader such as Picasa for importing and organizing
• do basic RAW adjustments and cropping in your camera maker’s RAW software if available
• use GIMP for further editing tasks

The main takeaway from the community is that fully free tools may feel fragmented and time-consuming, especially if you want a smooth RAW workflow with print preview, metadata, and watermarking. Several responders recommend reconsidering the “free only” requirement because your time and ease of use may be worth more than the savings.

If you can spend a little, low-cost commercial options mentioned were Adobe Photoshop Elements and Bibble, both suggested as capable single-package solutions for most or all of your listed needs. Bibble may need a plugin for watermarking.

So: free is possible with a multi-app workflow, but for convenience and a more complete RAW workflow, an inexpensive paid editor is likely the better fit.