If you are on Windows, Android, or macOS (and you don't want to compile from source), purchasing is the way to go. Here is the official process:
Open GCompris, navigate to the "Settings" or "Info" menu, and click "Activate." Type the code exactly as provided (pay attention to dashes and capitalization). gcompris activation code
Schools managing labs with no internet often use a legacy version that required a numeric code. This is obsolete. For school networks, use the portable USB version from the official site. No code required. If you are on Windows, Android, or macOS