Like I said before, I'm not an expert on this, nor am I a past user of Lotus Agenda, but based off what other users have said about it and what I saw in the patent, there are differences. At a glance, it sounds the same, but hey, we're talking about law stuff, so being nit-picky matters.
1)
Lotus Agenda uses freeform entry to provide a way of inputting data and then filtering. The freeform input is used as a command with integrated data. Like a natural-language style command console.
From reading
http://guterman.com/guterman_clips/..._HowItWor/guterman_clips_agenda_howitwor.html
it seems that Agenda actually would be a very early implementation of sorting by tags or smart playlists/collections/db-views/whatever-you-want-to-call-it.
The "See Wendy on Tuesday 3pm" example, in Lotus Agenda, would let you tag Wendy as a person, but until you do so, would not actually know it's a person. A "when" field exists by default so it'll capture one date automatically from the phrase.
Apple Data Detectors (ADD) takes existing data and tries to infer meaning by itself so that you can insert data extracted from other data. (as in, NOT a command console) With a simple example of "See Wendy on Tuesday 3pm", both ADD and Agenda will infer that "Tuesday 3pm" is significant. But ADD should be able to infer "see wendy" as significant too on its own, where Agenda will depend on you organizing "wendy" into a field first. That "see" is a verb will never be taken into account in Agenda.
From the user's standpoint, and for a simple example and overview, the two technologies appear to be the same and in many cases will act the same once the environment is set up. But the underlying mechanics are completely different.
Given that Lotus Agenda was created in the DOS era, that's kinda cool that they got this going, but ADD is by far more advanced.
This is kind of similar to the difference between the iPhone Voice Control and Dragon Dictate. They're both speech recognizers, but completely different usage. Dragon is primarily freeform which is much harder to implement, and hence lower accuracy. Voice Control is easier to implement and higher accuracy, but a heavily restricted command space. They're both awesome in their own right, but how awesome they are depends on if you're picking the right one for the task.
2) Oh, one more difference, there's this thing about this service being provided by a server in Apple's patent for integration amongst multiple services/apps. Lotus Agenda doesn't export its services simply because you're on DOS. You have no other running apps.