is basically considered a person who uses the Coolite Toolkit inside of Visual Studio.
The following quote from the License Summary provides more information, see http://ext.net/license/
The Professional Edition is licensed on a per developer basis. Each individual who uses the Coolite Toolkit for development purposes must obtain a Coolite Professional License to do so. The Coolite Professional License also grants a royalty free runtime license, which means you can include the Coolite Toolkit in your product and sell an unlimited number of copies of your product without a royalty fee. The only requirement is that one Coolite Professional License is aquired for each developer working directly with the Coolite Toolkit in an IDE, such as Visual Studio, Visual Web Developer, or similar.
If you have 4-5 Developers on your team that will be using the Coolite Toolkit, then the Team License would be the best option.
The full text of the Professional License is available at http://ext.net/license/Professional/
I hope this helps answer your questions. If you require any further clarification, please let us know and we'll be happy to assist.