Brickmaker
This is great! Can I make variations and sell it?
Yes!
You can do whatever you want with this file except resell this exact .blend! The results you produce is free to use in any commercial way.
How do I speed up the render with this material?
Since the material is 100% procedural, there is a lot of math going on and that will take time.
My suggestion is to always bake the textures when you feel you have found a satisfied result. Then it will be as fast as any other PBR texture out there.
Does it work on more than simple planes?
Yes,
The material is completely UV based, so as long as you have a good UV map that fits a creation of brick walls... this material should work as well.
Is it seamless?
Sorry to say... no!
If you want it seamless, you have to go the long way by using Photoshop or GIMP, create some offset and do some smooth/cloning on the bad edge.