Everyone seems to have their own definitions of "open source", the more I interact with people on here and in this space the more confused I get on the subject. I would say yes it is but I am not the arbiter of the definition. The repo is here

GitHub

GitHub - boshi-chan/nostr-monstr: Svelte Nostr Client with Monero Integration

Svelte Nostr Client with Monero Integration. Contribute to boshi-chan/nostr-monstr development by creating an account on GitHub.

its linked in my bio and on monstr.land itself so I didn't think it was necessary to link it in response to the question. Frankenstein, as in, Frankenstein's monster, a creature stitched together haphazardly. Monstr was created with llm's and my basic understanding of building websites. That's how I perceive it, I am not a professional, just a guy with an internet connection who got bored, its not a polished product. Ergo "frankenstein code"