This page doesn't include the original game data. Pick your own ultima4.zip (the DOS version of Ultima IV, which Origin released as freeware). It stays in this browser's storage — nothing is uploaded anywhere.
Drop ultima4.zip here, or
This fetches the game file from a third-party host through a small relay run for this site, checks it, and keeps it only in your browser. The game remains the property of its rights holders.
You don't need to unzip it. The xu4 project links to a download of the DOS version.