Maybe this is incredibly unfair of me, but I immediately discount any plugins that only let you download via a zip. There's no excuse for it not to be on Github, completely in the open.
If the last commit in the repository was more than 6 months or so ago, there's a decent change it's out of date, but I still might take a quick look. Any repository not updated in 12 months is immediately discarded.
Once again, no real excuse not to test code with JS these days. There's a plethora of libraries and resources available. Tests let me know with confidence that this plugin does do what it says it does. No tests = discarded, with the slight exception of some plugins or polyfills. For example, this Full Screen polyfil by Sindre is an example of a library without tests, that I'd be happy to use.