Pure maple syrup isn't toxic, but it's concentrated sugar — only a trace, rarely, if at all. Skip 'pancake syrup', which is artificial and even worse.
Real maple syrup is boiled-down tree sap — essentially natural sugar with trace minerals. It's not poisonous, but it's so sugar-dense that any meaningful amount is unhealthy. Imitation 'pancake syrup' is high-fructose corn syrup with flavoring and offers even less reason to share.