it's kind of time consuming to play because in order to do so you have to unpack your game and set the cards aside in order to reference them (ie Condition cards, Spell Cards, Mythos cards).
Or you could photograph/scan those cards and keep the images on the computer you use for VASSAL. You only have to do it once, and you can share the images with your playing group.
FFG are just trying to protect their copyright, and I think asking for some cards to be redacted is a reasonable compromise. There are some companies that don't allow VASSAL modules at all.