Well, it seems that PubSub.com is live again -- over three years after we took it down and handed all our assets over to our creditors in June of 2006. Frankly, I've been wondering what has been taking the new management so long to relaunch the system. PubSub.com was the first "real-time search" engine on the web and given all the attention that real-time search has been getting over the last few years, it is amazing that more effort wasn't put into getting the service retooled and up sooner. Although PubSub V1.0 was widely recognized as the first in its field (even though few people at the time recognized the importance of that field...), PubSub V2.0, as a late entrant into a crowded field, may be seen as simply "yet-another" real-time search engine...
I have no idea if they are using any of the old PubSub.com code but would be surprised if they weren't. The prospective search system that we built for PubSub was the best technology in the market at the time and probably would still be the best among those systems that are currently in public use. In any case, PubSub V2.0 is a somewhat different offering than PubSub V1.0 was. They have added a traditional retrospective search system (we had been experimenting with Lucene for that) and they are now provide streaming updates to HTML pages (something that we had implemented with technology from KnowNow, the company that first popularized "hanging GETs" and with whom we had been planning to merge. Unfortunately, issues caused by a disgruntled ex-employee and apparently irrational investors caused us to cancel the merger and close shop before exposing the live-update capability.) -- PubSub V1.0, as released, had only provided real-time updates via Atom/RSS feeds and XMPP PubSub streams. I can find no evidence of support for syndication feeds or XMPP on PubSub V2.0
It will be interesting to see if PubSub.com V2.0, after so many years of letting the competition get ahead, will be able to build a market for their service. They have lost the "first mover" advantage, but may still be able to have some success. Time will tell.
ex-CTO and founder, PubSub.com V1.0