It does look like an attempt to obfuscate code. And the php source code at that url just displays a form with a password box, but there's no "action" to the form, so I don't see how it would do anything. Also I don't understand how having just the url for the plugin code would run the php code. It seems to me it's more like someone working on a hack, or someone didn't know what they were doing (but it's also possible I just don't understand how it's meant to work

).