We are taking the files from its official repository.
You can see that in the source code of the website
<meta name="generator" content="Discourse 2.2.4 - https://github.com/discourse/discourse version 63dbac786fc4e9c575d12de6c5531a90f090555b">
The official way to support Discourse is by using the Docker images they provide. A different way to deploy the application doesn't support the methods they have, that's why we have that guide to explain how to upgrade it when you are not using its official packages.
Another alternative would be to use our containers that allow you upgrade the application easily.