Hello,
You can use some functionality separately from Kentico, but usually our customers use Kentico as a development tool. You can also use the ASPX approach to create pages, so the main work is done in VS, but Kentico is still the basic frame of your application and VS is a mere tool. As I mentioned earlier, the most common way to develop a site is to use Kenticco and VS just in case of customization or developing custom webparts/controls. You can find a comparision of those two approaches in the following
documentation.
Kentico is a common .NET application, so it uses all the mentioned (Master pages, CSS style sheets, ascx files...).
There is no standard way how to add Kentico to an already existing website. There are some
approaches, but it usually causes more troubles than good and that is why we recommend to built the site in Kentico from start.
If your requirements don't exceed the limitations of the free license, you can use it for commercial projects, but you have to include "
Powered by Kentico"
logo or footer. You also don't get phone and e-mail support with the free license. You can do all the development and testing on the free license.
Best regards,
Boris Pocatko