In order to get a license it seems there is a document FNP_LicAdmin.pdf However this is 253 pages long.Must I go through this document to find out how to get a license ? This seems quite extreme to me as I want to use the community version of MDK5
The file FNP_LicAdmin.pdf is the complete manual for the FlexNet Publisher. It explains all the details of this license server in case you need them.
For a standard license server installation, you should follow our Licensing User's Guide:
https://developer.arm.com/documentation/101454/0110/License-Management
For the FlexNet server installation and retrieving the license.dat file you can find the details here:
https://developer.arm.com/documentation/101454/0110/License-Management/FlexNet-Publisher-Setup--Server-?lang=en
This page explains how to setup the FlexNet license on the client side (in µVision):
https://developer.arm.com/documentation/101454/0110/License-Management/FlexNet-License-Setup--Client-?lang=en