This plugin has not been updated for a while. I have released a premium plugin, tinyIP, for the same function and it is tested with WordPress 4.0, if you are interested.
Hi there. The plugin doesn’t actually prevent logins. What it does is deletes the “session” of the previous browser logged in with the same account. This is meant to deter users from sharing their user name because it might kick them off the site. They can just login again, but that would kick the other browser off the site.
tinyIP might be a good solution if you need a more strict enforcement. I haven’t taken a look.
We have recently helped a custom to tweak WP Bouncer to be a bit stricter and basically disable logins after the first one in any given 24 hour period. This is super annoying for both legitimate and illegitimate users, but if you’re interested I can share that code.
