Luce is a plug-in written by Amico Perry. An Original software is Luce plug-in.
He published the source code of Photoshop version. So I could write this Gimp version.
Gimp2.8
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
See this link for more informations: http://creativecommons.org/licenses/by-nc-sa/3.0/
Please read README.txt or COPYING attached with distributed files.
Source code license is CC-BY-NC-SA. But a image you created is completely free even if it used for commercial purpose.
copy executable binary to gimp's plug-in directory.
and restart gimp. For more details read attached readme file.
Menu->Filters->Light and Shadow->Luce...
Windows
Linux
Mac OS X