1) You can use Asset Custom Fields for this, which can be set up under Configuration\Asset Pages. You can then Edit individual assets to input this value, or use the Mass Edit Assets option in the Assets tab to input identical values for multiple assets at once. If the assets don't yet exist in your database you can use the
Asset Import Template for this. In a future release we're adding a functionality that will allow the updating of existing assets using this template.
2) AD information is currently only retrieved from Windows computer assets unfortunately. Scanning AD information from non-Windows domain joined assets has been requested before and is already on our customer wishlist. We've moved this topic to the wishlist section in this context. We don't yet have an estimated release date for this though.