It has some fancy features to allow for custom heating presets among other things. Also, it means you can easily repair/modify the hardware for whatever reason you might come up with.
It has a display and even bluetooth. The Firmware is open source. The schematics are available.
Imo open source is not that important for an iron unless you want to add a klingon translation. But the iron is pretty good, although it is often rather >50 bucks including shipping.
Open source is good because it means it can be maintained even if the manufacturer shuts down. One of the biggest issues with keeping older tech alive and in a useful state is proprietary firmware.
Thanks for the suggestion, I was looking at buying another soldering iron. I'm using a really obscure brand one that I got from my dad and that I have been using since I was around 8 (30 years ago).
I can only get replacement tips in South Africa so was looking for something with more support.