Yeah there is the Kaldi backend for caster, which I've tried on my Mac machine, since Dragon isn't a thing on Mac. Unfortunately it's not nearly as good :-(
I'd like to try to record my usage of Dragon that I could fine-tune my own model, but it's harder to get around to hobby coding projects like that now that coding is more of a pain in the ass.
The unfortunate reality in my case is that using Dragon is the least frustrating way to keep working. I don't think closed paid ASR models will stop being noticeably better better than three open ones until the state-of-the-art error rate is basically zero.
I do like that caster is open source where talon isn't, but preferences like that are pretty low priority when say your career is on the line.