When using a custom font from a metric file font-weight does not seem to have any effect.. The font is of 1px width even if the weight is set to bold bolder etc...
Does your custom font actually contain the glyphs for the font-weight you want to render? If not then add those to your custom font and it should display correctly. BTW, unless you are really sure its a bug it is generally preferable to ask questions on the fop-user mailing list regarding the perceived problem first. The issue of font-weight and custom fonts was previously discussed on that list.
FWIW: the handling of relative font-weights was far from complete in 0.93, in some cases outright erroneous. I've recently committed some small changes to the trunk that should partly solve it.
resetting P2 open bugs to P3 pending further review