SoftLayer_Software_VirtualLicense is the application class that handles a special type of Software License. Most software licenses are licensed to a specific hardware ID; virtual licenses are designed for virtual machines and therefore are assigned to an IP Address. Not all software packages can be "virtual licensed".
SoftLayer_Software_VirtualLicense's service allows you to retrieve the hard-copy license file for a virtual license, if one exists for your license instance.
You can also retrieve the subnet that the IP to which a software virtual license is licensed upon exists in, as well as the software description that this virtual license is for.