Hi,
You can run multiple child portals using a single license.  For example, if your live domain name is mywebsite.com then you are able to use the module on the following domain Urls using a single license:
www.mywebsite.com
mywebsite.com
test.mywebsite.comup
dev.mywebsite.com
mywebsite.com/childportal1
mywebsite.com/childportal2
mywebsite.com/childportal3
If you point a different top level domain (tld) to the child portal it's no longer considered a child portal.  So if you point dns for a different tld  www.myotherstore.com then it's no longer a child portal and will require another license.  Each unique tld requires a license.
Here is a link to our license policy:
http://www.smith-consulting.com/Support/Policies