Will you clarify "system neutral"?
In my experience, some people use it to mean neutral to D&D-esque games (e.g. using HD but not more detailed stats), others further distance themselves by using mostly verbal cues but still include things like random tables that assume people have dice associated with specific systems (e.g. if I'm playing GURPS or Shadowrun, I'm not guaranteed to have a d8 or d%), and some are even further removed.
I feel like "a system neutral adventure for your favourite fantasy dungeon game" is a pretty clear statement that doesn't really need much extrapolation, but sure.
The closest the adventure gets to any kind of system is using the term "make a Save", which you can interpret in whichever way suits your system of choice. All of the adventures from this drop will come with monster stats for B/X, Mörk Borg, 5e, and The Vanilla Game in a separate download but again, you can safely ignore them if you have better ideas for mechanising the parts of the adventure you think need to be mechanised.
As far as specific dice go Google has a perfectly adequate dice roller, but I'd expect that anybody who knows what GURPS and Shadowrun are has access to at least one set of basic polyhedral dice.
