This is a plugin which adds a grouping option to ACF fields. You can use it to group fields that go together, such as a URL and link text field. This also works as a simplified version of conditional requirement. In this example, adding a Link is optional, but if you add one, both the URL and link text will be required.
This concept is similar to a repeater field which doesn't allow for repitition.
It does not currently support ACF version 4.
This plugins was created using the Advanced Custom Fields field type template repository. As such, there is a bunch of boilerplate code that is not currently used.
For more information about creating a new field type, please read this article.