Is there open source or free software to use my touchpad as absolute touch? I'm running OS X Yosemite, and don't want to spend money on a Wacom tablet. Is there free software or code that can disable the acceleration of the touchpad so I can write effectively with a stylus?
I just found a app called Inklet.

I did not try it my self, but will consider it for any pen drawing work where the use of mouse or trackpad is difficult.

It does cost $20, but it might be worth, but there is a free demo version to try first.