As far as I can tell: no, unless GitHub takes taking excerpts from works too far and redistributing them without the licence attached. But nobody else is allowed to deal in those excerpts then, except via the original licence, so, likely not.
But 4-clause BSD and similar advertising clauses are _probably_ affected, and Apache 2 _when_ a NOTICE text file exists is _very likely_ affected. (Maybe even without; the Apache 2 licence requires giving recipients a copy of the licence text, too.)
But 4-clause BSD and similar advertising clauses are _probably_ affected, and Apache 2 _when_ a NOTICE text file exists is _very likely_ affected. (Maybe even without; the Apache 2 licence requires giving recipients a copy of the licence text, too.)