Their business model allowed for greater ease to actually download and run unregistered/unlicensed copies, but higher costs with per-core licensing and clauses which required (i.e.) the per-core licensed OS plus the per-core licensed database if you wanted to use the latter.
It was both easier to run for free and way more expensive to run in legal compliance.
I've never heard of Oracle Linux needing a license key anywhere before. Can you provide a link to somewhere that talks more about that?