Simon,
Okay, now I understand. I've never looked at the search package in detail, so I wasn't even aware of that bit of code. I've fixed the problem, which requires changes to both openfts and the openfts-driver, so I will be releasing a new version of openfts soon.
Specifying all of the stop words in advance is not practical, as there can be hundreds of stopwords, and if your doing multilingual searching, each dictionary can have its own list of stop-words. I think the way it is implemented now is the most reasonable.