I think it's from IDA. For example see screenshots here: https://www.hex-rays.com/products/ida/6_0/.

There are similar reverse engineering tools that are open source such as:

- Ghidra: https://ghidra-sre.org/

- radare2: https://rada.re/n/radare2.html

From the author: "the x86 disassembly comes from IDA, the VM disassembly is literally in notepad++ and generated by my disassembler"

Replying just in case you get an answer, those are cool.