Good Day!
Our Company Client have bought MobileFirst Platform 6.3 server more than 3 years ago, but now need to use cordova Platform to create Client Mobile App, and with Java Adapter Restful. So we decided to use new Version MobileFirst Platform 8.0 , How the Process of Upgrading this server, does its need to pay for upgrade or its free to upgrade?
Regarding payment, you should obviously contact your IBM representative... this is stack overflow, and you're expected to ask here technical questions and not legal questions.
If you want to evaluate MobileFirst Foundation 8.0, you can start either from a local Developer Kit, or from a free trial on Bluemix. See here: https://mobilefirstplatform.ibmcloud.com/downloads/
For upgrading your project from 6.3 to 8.0, see here: https://mobilefirstplatform.ibmcloud.com/tutorials/en/foundation/8.0/upgrading/