Hi Nico,
The link package in the URL is a document wrapped as a file. You can import the file by right clicking a existing module, and then use “import document from file”
Note: You need to have the same version of the mendix modeler, as in where the package is created (6.7.1) or update it yourself (Mendix.Modeler.Packages.LoadProjectException: The package could not be imported, because it was created with version 6.7.1 of Mendix Modeler. Please open it in any version in the range from 8.12.0 to 8.18.99 first.)