CMSimple is an open source project under GPL 3, for free use, also for commercial usage.
A link to cmsimple.org in the template (Powered by CMSimple) is not mandatory, but highly appreciated.
The license terms of templates and plugins may vary and depends on the provider. This applies no for the plugins, included in the download.
It is not allowed to publish CMSimple-based projects under the name "CMSimple" or "CMSimple + version number", which could be confused with the original CMSimple.
In all core files must be included a clear indication of the source CMSimple, with the URL "www.cmsimple.org", and a reference to the GPL 3.