Is the touchpad driver in the macOS kernel? If yes, the kernel itself is open source, would it be crazy to try to extract the driver from there and make it Linux compatible?
Other question: When are you actually using the touchpad? I use my notebook 99% of the time with a screen + keyboard/mouse.
Next question: Can we get to the level of a Macbook touchpad only with software? Is there no magic sauce inside the hardware itself? How does the touchpad feel when installing Windows or Linux on the Mac?
AFAIK macbook's keyboard and touchpad has a dedicated chip to handle user interactions and is possibly part of the firmware. This explains why it works on Apple EFI level and it works smoothly even on high CPU load.
I salvaged a 2010-model MacBook Pro trackpad, soldered on some USB wires, and made it external. I was actually more interested in the keyboard, but discovered that I needed both because the USB controller is on the trackpad.
I use a 1st gen "Magic Trackpad" that works great with my hackintosh. Maybe there's special hardware in a MacBook, but the OS seems to be able to work without it.
I can only speak for myself. But in now 7 years I never connected a keyboard or mouse to my 2011 MBA. It's keyboard+Touchpad is just so good that I don't need it. Even when I connect to an external display.
I'd say no. In my experience other Companies aren't even able to recreate the smooth surface + 'clicking feel' of the Apple touchpad, which is what I value the most. I suspect that they can, but aren't legally allowed due to patterns.
I tried running Linux and Windows on a 2009 MacBook. Touchpad felt crap compared to on OS X. Pretty sure the Windows experience was better than the Linux one, though.
So software is certainly a part of it.
Edit: This is just considering basic movement of the cursor.
Other question: When are you actually using the touchpad? I use my notebook 99% of the time with a screen + keyboard/mouse.
Next question: Can we get to the level of a Macbook touchpad only with software? Is there no magic sauce inside the hardware itself? How does the touchpad feel when installing Windows or Linux on the Mac?