I don't disagree with you on this, but I just want to clarify something: Katz ripped off ARC, that much is clear. But on the other hand, ZIP was a brand-new format that had some differences from ARC. Among those differences is that Katz made the format open, something SEA hadn't done with ARC. This helped ensure its broad uptake as a de facto standard that's still used to this day.

I don't think what Katz did in SEA saga is worth defending, but I think we have to delineate the two formats. As Phil Becker of eSoft says in the clip, the reason that Katz's software ultimately won out was that he was more adept as a businessman—and the open nature of the ZIP format was a good example of that.

Don't forget, that this was also in the middle of the various look-and-feel lawsuits that were going on at the time. Lotus vs. Paperback Software, Lotus vs. Borland, Apple vs. Microsoft, Stac Electronics vs. Microsoft, etc.

Also, remember that PKarc was popular because it was faster than Arc. The feeling in the BBS community at the time were feeling a bit of rage, that a superior product was being killed through the courts. So when PKzip came out, which was not only faster, but had a better compression ratio, combined with the general sentiment in the community that were fed up with look-and-feel lawsuits, doing a mass conversion from arc to zip was also a form of public protest.