Interestingly, ViennaSHE is not just a free, multi-dimensional semiconductor simulator (using Spherical Harmonic Expansion of the BTE) , but a suit of TCAD tools. The complete package can be found at
I checked the website. From the description it looks like it is a multi-diverse solver from elasticity to other problems involving partial differential equations (kinetics? I don't know).
What I could not see was a good set of examples showing how the software was successfully implemented. As you state probably the memory problem made it not so popular.
Concerning the huge memory requirements (especially, for high number of moments or expansion series order in 2D/3D), this memory can be solved by searching for efficient algorithms . Interestingly enough, the developers of this software and their supervisors (in TU Wien, Austria) are actually scientists in mathematics, as far as I know. Why they didn't make enough research about this point?