This resource doesn't load as a plugin, because it's not a compiled jar file.
It's just a zip file of source code.

When I let the dev know, their response was:
""
bro you add this zip into your plugins folder it will world like another plugins also do you dint see invsee ++ plugin it is also a zip file
""

Thats not how the server works bro. The server looks for jar files, not zip files.

For the record, even tho I know thats not how the servers, I did try it, and as expected, no plugins loaded.

That said, I'm rating this 1 star due to its not a runnable plugin and the dev gave a useless response when I tried to help.