Commercial softwares such as Adobe Bridge and Photo Mechanic allows you to easily browse your images and add metadata to them (eg tags and notes). This metadata will be save in the same JPEG file as IPTC metadata.
I am looking for an open-source or freeware software to achieve this, for Mac OSX.
ps: I don't want a software that needs to import all the photos to their folder in order to work.
ps: I am aware of other software (such as Pixa) that saves metadata in OpenMeta, but this metadata is not saved in the same JPEG file and can get lost when copying files to other file system formats. I am not interested in this approach.