If you're able to build Sweet Home 3D from the sources as indicated in the README.TXT file, you should remove lines in the Ant build.xml file that includes or moves the "build/Furniture.jar" file according to the kind of installer you want to build (for example if you want to build a Windows installer, you should remove the line 423).
If you're not able to do that, you can remove from an installed version the Furniture.jar file found in the installed folder.

Caution: if you want to distribute a modified version of Sweet Home 3D, its GNU General Public License obliges you to distribute the source code of the modified version.