This feature has been deprecated as of 15/10/2021 and will no longer work!
If you are one of the few that feel generous enough to donate when downloading jOeSU, you can unlock extra stuff in-game and try out yet-to-be-released content! (this is done simply by pressing the download button on the main page, giving you the option to donate)
You must have an Itch.io account linked for the key to work.
How to activate your key in-game:
In the top right of the Itch site, click the dropdown arrow and go to My library.
You should see jOeSU in your library. Click on the Download button.
Once in the download page, the URL holds your game key. Copy the part of the URL that would look like the highlighted text in this image to your clipboard:
After you've done these steps, open jOeSU and click the Support button in the main menu (at the bottom). Voila - all done, thank you!