1. Please explain me what you'd like to know. Router is one layer of SPA / PWA so you need it if you want to make one. It's framework independent and I'd not like too add more dependencies to your project for such a small thing - even if it's powerful.
2. If you want to check it out quickly with minimal effort, play in your browser js console - it's there.
If this is 67 lines of code with zero dependencies, why do I need it as a dependency?
Regarding CDN implementation, why would anyone add an HTTP request to the page for 900 bytes?