As far as I can tell it is. But for the complete version of hacknet on steam (which is currently on sale) you could get it for $5, which is well worth it.
I just installed the itch version and tried to load my old save from the Steam version that has the DLC (I preferred a copy that I could run without opening the Steam client first), and got a message saying the DLC was not installed. The DLC isn't included with the itch download.
