That is the point with licensing of file geodatabases in ArcGIS 10.3.
The author protects the geodatabase by creating first a license definition file (.licdef file, which will provide settings for the licensing) and generating a licensed file geodatabase (by copying the source file geodatabase and its data and modifying some of its properties).
Thereafter, the author generates a data license file (.sdlic) for distribution. The geodatabase and this file will be shared to users. They install the data license and access the geodatabase with those restrictions that were defined by the author.
The .licdef file is an XML file which contains unique GUID for the datasets stored within the file geodatabase. Without knowing those IDs, you cannot re-generate the .sdlic file (which is a binary file) using the GP tool Generate File Geodatabase License.
If this would be possible, then anyone could re-generate the license file and protecting file geodatabase would become useless.