The overview at the beginning of this thread says:
Getting the 5.0 Connector Beta
Reminder— betas are pre-production software; please do not deploy this in your production environments! It is for EVALUATION ONLY.
Users can get the 5.0 Connector v5.0.306 preview beta by visiting the Zimbra Support Portal. Inside you will find a link in the Support Menu on the left for ‘ZCO 5 Beta’ to download it.
Later, the full Connector 5.0 beta will ship as part of the ZCS 5.0 Release Candidate. The Connector can be found in the web Admin Console in the Downloads tab.
In reality, the portal only has the RC2-based connector, though. Since our server is still 4.5.6 for a while longer I need the v5.0.306 preview beta connector. Does anyone have a link for that version?