Even though these projects have "discontinued" labels besides them it seems that some users are still confused and think they are being developed\supported. As they haven't been updated for years and are based on a technology which is dying off, there is no point to keep them on the "front page". We should still keep the forums categories, so one can still find useful information.
XIFF and SparkWeb should be removed from the Projects page (at the bottom). And from the Downloads page.
So, general consensus is that it doesn't hurt to have them around and they already have "discontinued" labels.