Hello! Sorry for the delay in answering!
Yes, the fact that I left the script files accessible is intentional! I did so both to share knowledge and because there isn't much to hide in such a small-scale, free VN anyway. ^^
I really don't mind if people have a look at the script, play around with it, learn something —in fact, I hope some people do and it proves useful to them! I've tried my best to document the code exhaustively with comments so it could be helpful and comprehensive to curious readers and fellow VN developers.
Scripting a full story and GUI can be difficult, and I hope that open source examples of completed VNs like this one may help a bit. There's probably nothing which is especially complex or impressive in the script of Sylvan Disappearance, but I still wanted to do my part! If anyone at all finds any use in some part of the script, I'll be very glad. ^^
Oh, the epistolary screen might be of use to someone! It's probably the most “complex” part of the code, and I guess it might be useful as a storytelling mechanic in other VNs. In fact, I'm planning to distribute the code of this system as a standalone recipe on itch.io and Lemmasoft in the near-ish future! I don't mind people reusing parts of the script entirely, as long as I'm credited.
The only thing I did protect and wouldn't want to see reused at all are the original art assets drawn by Hyanide.
The other assets are all free to use in some capacity (the full list of sources and licenses is in the Credits menu), so I did not protect them either. :)
Hope this answers your question, and that you enjoy the story!
Thanks for asking, this reminds me that I should add a note about this on the page and in the update I'll upload in a few weeks. ^^