Install On Mac OSX For Free
I open the Sweet Home 3D download web page at http://www.sweethome3d.com/download.jsp
and choose to download and install Sweet Home 3D the manual way which also happens to be Free.
You can download the Paid version from the Apple iTunes Store and you will get many extras such as many more 3d models and support.
The Free version can also have the same models, but you will need to manually import them into the Furniture Library yourself.