In addition to the story of the product VisiCalc, there is the related saga of the relationship between the two companies most involved, Software Arts and Personal Software.
(The account here is based upon my recollections and notes. Others may differ.)
As the success of VisiCalc became apparent in early 1980, Personal Software proposed a merger with Software Arts in mid-March. Around the same time, Personal Software decided to obtain venture capital funding, which it received in May of 1980, and brought in a new person to run the company. Talk of merger stopped (to the surprise of Software Arts, which was working hard to prepare for it) and relations between the two companies soured. Exactly how this change came about within Personal Software, I don't know. The talk from senior Personal Software executives, as we heard it, turned to how to lower royalty rates and then to a buy-out by Personal Software of VisiCalc outright for a lump sum. Animosity between the top executives at the time led to a change to negotiations done by second level executives. Negotiations moved slowly.
Personal Software renamed the company to "VisiCorp" in early 1982, and most of its products were "VisiThis" and "VisiThat" and advertised as "from the same people who brought you VisiCalc". In 1981 it started development on a Xerox Star-like system called VisiOn which was pre-announced in the fall of 1982. They developed both the system software and application products for it. VisiOn was shipped in December of 1983.
Software Arts, aware of the need to have products other than VisiCalc for the days after a deal would be completed, started developing other products and put in place production, marketing, and sales teams. Later, and as VisiCalc sales started showing the effect of Lotus 1-2-3 (which became the dominant spreadsheet for years until overtaken by Microsoft Excel after the emergence of Windows), it also pursued corporate buyout opportunities that came its way that would give the founders liquidity and the product development additional financial backing.
VisiCorp sued Software Arts in September 1983, much to the surprise (and dismay...) of us at Software Arts. The charge was being late delivering various versions of VisiCalc Advanced Version. They asked for tens of millions of dollars in damages, and judgment that they didn't have to pay Software Arts royalties for VisiOn's spreadsheet program. A pending acquisition of Software Arts by a large company was put on hold and then became impossible. To protect itself in the legal battle, Software Arts countersued in early 1984, claiming breach of contract. The lawsuit went to a preliminary injunction hearing later in 1984, where the judge did not grant the injunction requested by VisiCorp. In the summer of 1984, a settlement was reached, with VisiCorp paying Software Arts some money for past royalties and giving up the VisiCalc (but not "Visi" alone) trademark. VisiCorp was eventually sold off to various players.
Summons announcing the lawsuit between VisiCorp and Software Arts
A history of Personal Software / VisiCorp can be found in a business school case from the Anderson School of UCLA. It is "VISICORP 1978-1984 (Revised)", POL-2003-08, prepared by Professor Richard P. Rumelt with the assistance of Julia Watt. As of May 2009, there is a copy on the web on the UCLA web site.
Development continued at Software Arts during and after the lawsuit. Products including Spotlight, a pop-up program similar to Borland Sidekick, and TK!Solver for the just released Apple Mac, were created and shipped. A background email program code named Wildfire was worked on by Bob Frankston and others.
After searching for a corporate partner for many months, Software Arts' assets were sold to Lotus Development Corporation, the creators and publishers of the 1-2-3 spreadsheet, in the spring of 1985. Lotus sold TK!Solver to another company, and later released Spotlight and Wildfire as Lotus Metro and Lotus Express. Lotus decided not to continue publishing VisiCalc.
Bob went to work for Lotus, and I, after a brief time consulting to Lotus, founded Software Garden to develop the Dan Bricklin's Demo Program (with Lotus' blessing).
For the players, it finished with a sad ending, but it was a fun ride while it lasted. I still hear from ex-Software Arts employees about what a great time it was and how much they learned. And in addition, the product we made was good and important enough that here, decades later, people like you take the time to read about it.