Sonic Adventure Dx Internet Archive -

Sega is notoriously inconsistent with enforcement. They have DMCA’d specific ROMs in the past but generally ignore Sonic Adventure DX because:

The Internet Archive (archive.org) is a non-profit digital library that aims to offer "universal access to all knowledge." While it is famous for the Wayback Machine, its software collection has become a vital repository for "abandonware"—software that is no longer sold or supported by its copyright holder. sonic adventure dx internet archive

The Internet Archive hosts several iterations of the game, each serving a specific niche for fans and modders: Sega is notoriously inconsistent with enforcement

Until then, the Chao are waiting, and the Internet Archive has the key. the Chao are waiting