Free • Open Source. Krita is a professional Free and open source (FOSS) painting program.
Doxy's Brush Dump
Easy Paint Tool Sai Brushes
It is made by artists that want to see affordable art tools for everyone withith concept art, texture and matte painters, illustrations and comics. Very advanced program that is absolutely free, only downside is that it's not as lightweight as SAI. It has animation features, fullscreen support, and works well.
Paint Tool Sai for Mac Equivalent app - Pro Paint for Mac is available for OS X 10.8 +, iMac, Macbook Mini, Macbook air, Mountain lion, Macbook Pro, Yosemite, mavericks, EI Capitan, macOS Sierra, Big Sur.
Paint tool SAI Mac is considered and recommended by the professionals in the field of digital painting. It is recommended by the professionals because it has almost every feature that is required in the field of digital painting. This paint tool gives the opportunity to create digital painting that gives the look of professionals and a piece of art. If it is set side to side with the other painting tools, we can clearly see the difference between them. Pain tool SAI is loved by each and everyone on a windows PC because of its tremendous and fabulous features. It has a overwhelming and light painting feature, furthermore, the painting by using this tool is very easy. You get the result entirely you are in need of. Due to its easy and simple features, a person who has just access to this painting tool can easily and comfortably make the digital painting as it is designed this way. It also consists of a 16bit ARGB channels and Intel MMX supported technology. We often see that bug issue is quite normal while using these tools but in paint tool SAI has a protection feature too which is used for termination of bugs.