Many schools and workplaces block gaming websites. However, GitHub is a platform used by developers for coding and collaboration. Network administrators often leave GitHub unblocked because it is essential for educational and professional work.
By hosting the game files on a GitHub repository (or a GitHub Pages site), players can access the game through a link that looks like a coding project rather than a game site.
"Eagle Craft" typically refers to a web-based version of Minecraft built using JavaScript and WebGL (often based on the "Eaglercraft" project). Because it runs entirely in a web browser, it became popular for playing Minecraft on devices where the actual game cannot be installed, such as Chromebooks or restricted school computers.
You might wonder: Is Eagle Craft illegal?
Eagle Craft is a fan-made open-source recreation. It does not use Mojang's actual code or assets (though some forks include textures that resemble Minecraft). The legal status is gray: