While there is not a hard limit for the Jive on-prem solution, the highest supported (QA'd) setting for attachments is 100MB. As such, I would recommend tested out any setting exceeding this limit. Additionally, if you encounter any issues as a result of this increase I would recommend reverting the setting.
Yeah we currently have it set to 2gb and if the users connection isn't great they can get issues but that's as expected I think.
Now I know there's no hard limit we'll decide whether to test a higher threshold or not.