Which is why it's bad writing.
"Unblockable killing spell" is the kind of thing that pops up on a middle school playground because every kid wants to have the trump card in make-believe and the last kid just cast Meteor.
Eragon is a contemporary-ish book and has killing magic that can kill normies by the dozens/hundreds, but other magic users have to do more than play rock-paper-nuclear-option.
I would be surprised if a cartridge being discontinued would kill an open source project like this. They could switch to a different cartridge.
I'd assume they're doing the one for now because it's cheap-ish and has widespread availability. There's little reason not to expand to other cartridges once the rest of the printer is more stable.