It is an apple.

An apple is more than the actual fruit. In our language, we name things. And we name drawings of familiar forms, such as apples, with the words from the language.

Sorry. Show me a drawing of an apple and I'll use my language to identify what you've shown me--the word my language provides for that drawing--tough luck--is apple.

All that said, I love the art! I love the written "This is not an apple." It's humorous. and even ironically so