Why it matters when you are writing
The routes differ in who pays and where the article lives. Gold makes the version of record free immediately, funded by an article processing charge that can run into thousands. Green costs nothing and puts the accepted manuscript — post-review, pre-typesetting — in an institutional or subject repository, often after an embargo. Diamond journals charge neither readers nor authors, funded by institutions or societies. Hybrid journals sit behind a paywall and sell open access per article, an arrangement many funders now refuse to pay for.
Licensing determines what readers may do beyond reading. CC BY permits reuse with attribution and is what most funders require; more restrictive variants limit commercial use or derivatives. This matters concretely for anyone wanting to reproduce your figure in a textbook or feed your text to an analysis pipeline, so it is worth choosing rather than accepting the default at proof stage.
Check your funder’s mandate before you submit, not after acceptance. Many national and charitable funders now require immediate open access with a specific license, and some prohibit the embargo periods a hybrid route would impose. Waivers for authors in low- and middle-income countries exist at most publishers and are underused, largely because they are advertised badly.
