It ain't much, but it's still pretty cool and interesting.
"With the permission of Adobe Systems, the Computer History Museum has made available the source code for Photoshop version 1.0.1, comprising about 128,000 lines code within 179 files, most of which is in Pascal, the remainder in 68000 assembly language. This the kind of code I aspire to write. The Computer History Museum has earlier made available the source code to MacPaint."
Note: At the time of writeing, the source code site is down.
Here is some screenshots of PS 1: http://creativebits....on_of_photoshop