The FLIP Fluids addon is a tool that helps you set up, run, and render liquid simulation effects. Our custom built fluid engine is based around the popular FLIP simulation technique that is also found in many other professional liquid simulation tools. The FLIP Fluids engine has been in constant development for over four years with a large focus on tightly integrating the simulator into Blender as an addon. It just feels like a native Blender tool!
It is licensed under the GPL3 and MIT license, which allows for free redistribution. This is a patch I created to allow using the entirety of the software without purchasing it. While this is legal, I recommend purchasing it from the developer if you have the means anyway, as this is a truly good product.