“Richard Stallman talks about the evil of copyright, and says we need copyleft to ﬁx it. At Berkeley, we just say ‘Go down to Copy Central and copy it.’” --Kirk McKusick, head of Berkeley Unix projectWednesday, January 16, 13But there was another element to the early spread of open source. Unix was the ﬁrst operating system that became divorced from theunderlying hardware. It ran on many different machines with very different architectures. Code from one machine couldn’t simply be run onanother; it had to be recompiled. With a standardized hardware architecture, PC software could be distributed in binary. Unix *had* to bedistributed in source form, because that was the only way to get the software to run. All of us spent time “porting” programs we’d received toaccount for either differences in hardware architecture or differences between various implementations of the operating system. In addition,because it was initially a non-commercial operating system, software was shared freely. Unix was developed collaboratively by hundreds ofdevelopers across many organizations. In an odd way, open source was a response to the problem of incompatibility.