It is safe ? I did not see the information from the developers (
This should be safe, but I would always recommend backing up your wallet before updating your client.
This repository is hosted on his own GitHub organisation, as it is currently only being used for temporary reasons. On release, the current repo on the Litecoin-Project org will be updated.
Xinxi Wang is a Litecoin Core Developer, and is currently working on rebasing Litecoin 0.10.4 to 0.13.1 (when released and tagged).