Dear Mohamed,
Thank you for your message.
It depens on the content on your sub-domains. If the content on your sub-domains is the same as on your main domain it is enough to purchase 1 Web Site License. 1 Web Site License allows you to run one live web site. The web site can have one main domain and any number of additional domain aliases that point to the same content as the main domain. If you run web sites with different content on sub-domains of the main domain these web sites are considered as a new web site and require additional license.
If the content on your sub-domains is different than on your main domain you need to purchase an appropriate number of the Web Site Licenses or you can purchase 1 Server License if you plan to run all your web sites on a single physical server. 1 Server License allows you to run any number of your web sites on a single physical server.
Each license is available in several edition with different set of features. You can compare the editions here:
http://www.kentico.com/cms-asp-net-features/Feature-Matrix.aspxYou can find our prices for each license and edition here:
http://www.kentico.com/Buy.aspxBest regards,
Michal Minarovic