Ok so RyanLand replied 😊:
And here is the GitHub of the project in case you want to check the code yourself or feed it to a mod code checker:
https://github.com/RyanLandDev/DFSchematics/
I hope so, I am not sure but it should be safe as RyanLand is a trustable member.
Maybe VirusTotal did that because it's a jar file? (it does that with 99.99% of minecraft mods)