The original Zork I, II, and III games are now available for free under the MIT license. This means they can be freely studied, modified, and shared. Microsoft has partnered with Xbox and Activision to preserve the Z-Machine engine that powered these classic games. The move aims to benefit students, teachers, and developers who want to learn from the code. Jason Scott, from the Internet Archive, has also been involved in granting this open-source license, making it easier for people to access and work with the games’ code.
Source: https://www.theverge.com/news/824881/zork-open-source-microsoft-xbox-activision