It's how the plugins are written. It's a real simple fix (a line or two of code) but since the vast majority of writers are on pcs, they don't realize they need to add this little snippet for macs. Some people have began including it (fredo for instance) and I've edited a couple of rubys to work right on mac but a couple of them are encrypted so I just deal with it (or keep the script unloaded until I need it for a particular session)
anyway, you might want to ask the writer to include the necessary code. I'm on a phone right now so searching the forum is cumbersome atm but there are threads here that outline what needs to be included.