The Backend that powers SpiceCRM is SugarCRM in its latest Community Edition Release. Nevertheless, we took the liberty to add some additional capability and are also continuously cleaning up some core elements. Yet the base is proven and up and running n thousands of companies as core CRM Systems that powers systems serving partially even very different purposes. It is built on PHP as the core framework supporting the latest PHP releases and all major database systems. It best runs on Linux but also can be of course run on Windows. Various Web servers are supported and open flexibility there. And with PHP being one of the backbones of the internet this is here to stay.
Contrary to SugarCRM we have removed all UX components and the backend serves as a true REST/SOAP Service provider.
In any case, we want to highlight that we are not an affiliate or partner of SugarCRM and that SpiceCRM does not leverage any commercial version or products of SugarCRM as a company. This is purely leveraging the Open Source Project of SugarCRM Community Edition that is the base and has been significantly enhanced and is continuous further developed as part of the SpiceCRM Project.