iToo Software offers a "Lite" version of their industry-standard Forest Pack. It is free for both personal and commercial use and provides many of the same scattering features.
For those open to switching software, Blender is free and its Geometry Nodes system offers some of the most advanced scattering capabilities in the industry. Conclusion multiscatter 1097 free
If the price of MultiScatter is a barrier, there are several ways to get similar results legally: iToo Software offers a "Lite" version of their