Thanks for the link to the Dev Hub. I posted a ticket about the "debug" feature not working properly.
I had the same problem with 1.8 that I had with 1.7, namely that pdfread was generating empty .lrf files. I tracked it down to an outdated libpng. pngnq wasn't working (silently dying while running inside the python script) and therefore the "page.png" files were not being downsampled and moved to N.png files. I would suggest adding some error checking code there (in the downsample function of the BaseOutput class) instead of relying on the existence of page-nq8.png implicitly like that.
FYI an .dmg installer for a libpng that works is here
Sorry for the confusion regarding "fork"... I meant a fork of the source code (i.e. you are taking over an abandoned or otherwise unsupported project) as opposed to multi-threading. But you answered my question anyway.