The "context-free"dom you reference here is purely syntactic. Linus here is certainly discussing the semantics of the language, since he is discussing reading

The "context-free"dom you reference here is purely syntactic. Linus here is certainly discussing the semantics of the language, since he is discussing reading and understanding the code. For that you need at least a (perhaps mental) syntax tree, of which there may be many for a given program, and which requires semantic context to disambiguate.