September was clearly quite unrealistic, from the perspective of a developer who was previously in the habit of making unrealistic project time forecasts.

NEVER believe anyone who says this, that etc. can be done in three months. I don't believe people who insist 'I wrote this and this in a weekend!' either. Yeah, you and that library that took three months to write. Six-nine months would make sense for a project like this, at least if you're planning on ending up with something worth using.