An anonymous reader writes: Microsoft, along with the Computer History Museum, has released the source code for MS-DOS 1.1 and 2.0, and Word for Windows 1.1a. Th DOS 2.0 was released for IBM PCs in 1983, and Word for Windows 1.1a came out in 1990. The museum has made the code available for non-commercial use with Microsoft's consent. They've also posted some historical information about the development of this software: '[In August, 1980], IBM had already contracted with Microsoft to provide a BASIC interpreter for the PC, so they asked them to investigate also providing the operating system. Microsoft proposed licensing “86-DOS”, which had been written by Tim Paterson at Seattle Computer Products (SCP) for their 8086-based computer kit because the 16-bit version of CP/M was late. When SCP signed the licensing deal  with Microsoft, they didn’t know for sure who the computer manufacturer was. Paterson said “We all had our suspicions that it was IBM that Microsoft was dealing with, but we didn’t know for sure.”  He left SCP to work for Microsoft in 1981. “The first day on the job I walk through the door and ‘Hey! It’s IBM.’” Microsoft originally licensed 86-DOS in December 1980 for a flat fee of $25,000. By the next summer they recognized the importance of owning it and being able to license it to other companies making IBM-PC clones, so they purchased all rights for an additional $50,000.'