Recently, Microsoft reopened the source code of MS-DOS 1.25, 2.0 and attracted the attention of the open source community. This is not the first time Microsoft released the source code of MS-DOS. In March 2014, Microsoft released the source code of these two versions through the Computer History Museum. However, at the time, a restricted license was used, and users were banned from other projects. Reuse these codes for non-commercial research, experimentation, and educational purposes only. This time, Microsoft is using a relatively free MIT license.
FreeDOS founder Jim Hall published an article yesterday, saying that Microsoft’s use of MIT licenses for MS-DOS source code makes a lot of sense, which means they are not only open source software but also free software.
Jim Hall explained, “FreeDOS started from an original source code base, independent from MS-DOS. Certain functions and behaviors of MS-DOS were identified and documented in the comprehensive Interrupt List by Ralf Brown, and we provided MS-DOS compatibility in FreeDOS by referencing the Interrupt List. But many significant fundamental technical differences remain between FreeDOS and MS-DOS. For example, FreeDOS uses a completely different memory structure and memory layout. You can’t simply forklift MS-DOS source code into FreeDOS and expect it to work. The code assumptions are quite different.”