Eudora -- first released in 1988 -- was the first industrial-strength email client designed to run on personal computers like IBM PC and the Macintosh; though there are still die-hard users of the program, the last version was published in 2006.
Qualcomm, the current (and largely absentee) owner of Eudora has teamed up with Silicon Valley's amazing Computer History Museum to publish the sourcecode for that 2006 version; under a permissive BSD license, untouched save for the removal of curse-words from the source code comments.
The Eudora release is accompanied by a lovely potted history of the program, including the origin story of its name (inspired by Eudora Welty's essay "Why I Live at the PO"); a remembrance of the program's days as "postcard ware" that led to thousands of thankful postcards being mailed to the program's original author Jeff Beckley; and an appreciation of the unique, powerful features that made it the killer app of the earliest days of the consumer internet.
The Qualcomm version of Eudora was originally available for free, and it quickly gained in popularity. To get a feel for the user community, Beckley called it “postcard-ware” and asked people to send him a postcard if they liked it. “I got thousands of postcards from all over the world. . . . There was this great feeling about the software, and everybody really loved it.”
“But,” Noerenberg recalls, “postcards don’t pay the bills.” He faced management pressure to stop spending money on a free product. “In 1993 I hatched the idea that if we could somehow convince Qualcomm there was money in an internet software business, we could turn this into a product and we’d get to keep doing what we loved.”
Eudora was soon commercialized as a paid version for $19.95. There was still a free version, now supported by advertisements. By 2001, over 100 person-years of development had been invested in the Windows and Macintosh versions. The paid version eventually sold for as much as $65, and it was aggressively marketed by Qualcomm.
The Eudora™ Email Client Source Code [Len Shustek/Computer History Museum]