I want to bulk upload discussions/ideas on the JIve page on behalf of the original authors. Is this possible in Jive?
Yes, via REST API.
https://developers.jivesoftware.com/api/v3/cloud/rest/ContentService.html#createContent(String, String, String, String)
Using Batch Operations with the V3 API
Core V3 API - Run-As Feature & Signed Add-Ons
Retrieving data ...