The authentication prompts are fixed in EDS 3.9.5. From the NEWS file:
============================ Evolution-Data-Server 3.9.5 2013-07-29 --------------------------------------
* E-D-S now uses Google's OAuth2-based CalDAV v2 interface for Google accounts added through GNOME Online Accounts or Ubuntu Online Accounts, which means no more password prompts. ============================
The authentication prompts are fixed in EDS 3.9.5. From the NEWS file:
======= ======= ======= ======= Data-Server 3.9.5 2013-07-29 ------- ------- ------- ------- ---
Evolution-
-------
* E-D-S now uses Google's OAuth2-based CalDAV v2 interface for Google ======= ======= =======
accounts added through GNOME Online Accounts or Ubuntu Online Accounts,
which means no more password prompts.
=======