It uses SVG as a describing language of drawing. Being a standard, SVG can afterwards be used by a large number of applications, widgets and libraries.
<InputDraw/> uses flash technology so almost everyone can use it. Remember that there are more installations of flash than windows.
You can use the non-commercial license for free, just download it on the <InputDraw/> site.
For commercial sites, you can also buy the license and receive the commercial package.