List examples of notable dissapeared source code projects/artifacts and have it publicly available

The question is do we have a well known example for source code that disappeared from the public domain and left a serious impact on the people involved (developers, users or society)?

These examples can demonstrate the necessity of Software Heritage.

Let's list in this task the examples we find and decide how to showcase on the website/wiki/docs.

Migrated from T2815 (view on Phabricator)

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