After obtaining the necessary access from Aurea, you would like to perform custom development and would like to know if there is any documentation on how to perform the code changes for Jive on-premise.
You can utilize the resources available in the Jive Developers Space on Worx community. If you don't have access to Worx, you can request an account. Additionally, you can refer to the publically available Jive Developers documentation.
Please note that helping with or advising on any code modification is out of scope for Jive Support. However, if you still need assistance, you can reach out to your Account Executive/Manager to arrange for a Professional Services engagement at an additional cost.