WHMCS is build on Bootstrap foundation and has core CSS files included, While WHMCS is mostly a backend design and automation it is even possible to use it as store front end. WHMCS will automate software or other files sales, payments and downloads in a smart and simple way. With extra WHMCS Licensing Addon you could sell software license with automatic license key generation, activation and reissues. The price of Licensing Addon is one time $99.95 including lifetime updates. And you will have all the benefits of well tested and trusted WHMCS platform itself to automate customer management, invoicing and support ticketing system. WHMCS itself use this module to automate there licensing management.