For background, an ECCN is the index number of a category of export-controlled computers, systems, and/or software on the US "Export Commerce Control List"
Dokan does not appear to be controlled under any category of the ECCL that I can find, so I believe its ECCN to be EAR99.
However, I only looked at categories 4 ("Software") and 5.2 ("Information Security"), as those categories appear the most relevant. As always with something potentially giving rise to criminal liability, it is advisable to consult with a lawyer to verify that I am not feeding you false information.
I am not a lawyer. I am not affiliated with the Dokany project, but its maintainer is in France, so very likely does not have direct knowledge of US export control requirements.
-Kyle H