It was an excellent tool. Unfortunately, the developers have decided to discontinue it, for understandable reasons. I quote:
"Some of you may remember that we posted a beta version of Keyword Manager 1.6 earlier this year, which was compatible with iPhoto 9.1.1. However, when version 9.1.2 was released, the beta version no longer functioned. This is because a number of the functions that Keyword Manager uses to do its work were removed from iPhoto in that update.
"Each version of iPhoto that is released requires us to rewrite the entire interface between Keyword Manager and iPhoto, due to the changes that Apple makes to the internal structure of the program. We'd like to stress that this is not unexpected nor in any way Apple's fault. It is just the nature of writing a plug-in for a program without a supported plug-in architecture.
"The economics of keeping Keyword Manager up to date has caught up with us and making the plug-in work reliably in the current version of iPhoto, and then the next one after that, would require a substantial investment in time and resources from our side, and even then it is not certain that we would get Keyword Manager working as well as we'd like."
Sorry to hear that - but thanks nevertheless to the developers for all the good work they did and the time they invested.