It means the card itself is homemade. It's unofficial and unlikely to ever be listed here. To list a card like this, you would have to have a complete checklist as well as details about when it was produced, etc.
From the FAQ:
Are unlicensed/Broder, ACEO, or reprinted cards allowed to be listed?
Cards of this nature may be added in limited scope.
For unlicensed*/Broder** cards, the following criteria must be met:
- The cards cannot feature any current players as they would presumably be under current player association contracts for use of likeness.
- The year of release must be known.
- A complete checklist must be known.
- The set must be placed into the "Unlicensed" category.
- The set should have "(Unlicensed)" placed into the set's name.