Synology has added Amazon Cloud Drive support, along with a few other minor fixes. The latest release is version 1.0-0378 which was released today (June 11, 2015).
Their release notes list the following changes:
What's New 1. Added support for Amazon Cloud Drive.
Improvements 1. Improved WebDAV compatibility.
Fixed issues 1. Fixed an issue where S3 subfolders might not be correctly displayed. 2. Fixed an issue where token expiration is not duly notified in certain conditions. 3. Fixed an issue where an expired access token might lead to a syncing loop. 4. Updated Yandex Disk icon.
While I could not specifically test for the fixes and I’ve yet to set up Amazon Cloud Drive in it, I did’t have any issues updating my two Synology NASs that have Cloud Sync configured. My test NAS, a DS212+ connects to Google Drive and Dropbox. My production NAS, a DS1815+ adds a connection to OneDrive in addition to the other two services.
This isn’t a critical update so there’s no rush to install it. That is, unless you want to use Amazon Cloud Drive or have been affected by one of the fixed issues.