[ShorsHammer]

Quite sure you are right, unless my memory is failing sitewide github search of codebases required a login. Searching for repo names without login was ok though.

Possibly it was only enforced for very generic search queries returning thousands of results but it has been around a long time, Github acquisition was only in October 2018.

[tbodt]

Sitewide code search has been used to find AWS keys and other secrets people have accidentally uploaded. The login requirement is so they can set meaningful rate limits.