Enlarge / The Apple Lisa 1, released in 1983. (credit: Apple, Inc.)
As part of the Apple Lisa’s 40th birthday celebrations, the Computer History Museum has released the source code for Lisa OS version 3.1 under an Apple Academic License Agreement. With Apple’s blessing, the Pascal source code is available for download from the CHM website after filling out a form.
Lisa Office System 3.1 dates back to April 1984, during the early Mac era, and it was the Lisa equivalent of operating systems like macOS and Windows today.
The entire source package weighs is about 26MB and consists of over 1,300 commented source files, divided nicely into subfolders that denote code for the main Lisa OS, various included apps, and the Lisa Toolkit development system.