Yes. Renders you create are yours and can be used commercially. The add-on code is licensed under GPL-3.0-or-later.

Instances are copies of a streak that share its look. Each one keeps its own curve, travel animation, color tint and brightness, so a group can move differently while looking the same. Change the look and every Instance in the group follows. Make them with Count in Add Streak (100 in about two seconds on an RTX 4090), with Add Linked Instance, or with Alt+D. They share one shader, so a whole group compiles once. Make Independent gives one Instance its own look.

Yes. Every streak comes with its own Bezier curve: select it, press Tab and shape it with Blender’s normal points and handles, and the volume follows as you edit. In Add Streak you can also set the path’s length and number of points, or start from a circle. A streak follows one open Bezier spline; Poly and NURBS curves aren’t supported (convert them with Curve › Set Spline Type › Bezier).

Use Cycles with OSL on an NVIDIA RTX GPU through OptiX, or render on the CPU. On AMD, Apple and Intel graphics hardware, use CPU rendering for this effect. Blender 5.2 or later is required.