Well, I wouldn´t try to implement the original K2 livesearch, and search for another solution, e.g. this one at orderedlist.com. Why? Because the K2 one needs many changes – in my opinion to many changes.
Another Option: The old K2 livesearch used in the early K2 releases.
And another thing: It would be nice to have (if you have bbPress integrated with WP) one search to search all…
Very nice Theme.. it looks a lot better than my attempt to let bbPress look like K2.
When will you publish it? Do you plan to put the code a plattform like Google Code to make development more accessable?
(Sorry, that my english is a bit crappy, it´s due to I don´t speak and write in english regularily.)
@ear1grey: Maybe I´ve got the plugin you want to have – some time ago I created a plugin like that for a bbpress+wordpress site which is no more online – I´ll search it on my HD and test it, and if it still works I´ll put it up for download…
