Is it possible to use this task manager on PC standalone (more details in the table of contents)?

Question

JavaScript

I found a kanban board that suits me in the back alleys of the web: https://wekan.io/
There is a "download" button on the main page of their site. When you click it, it takes you to github.
You can download the project files there.
1) Can I use this task manager on PC standalone?
Or did the developers put the files of this project on github, only so that others could modify the project for themselves?
2) Some project files have extensions:
.spk
.gz
What are these formats used for and how do I open them?
PS The project is written in JavaScript, Meteor framework.
The project is really worth it. Trello analogue. Maybe someone will like it too.