The Charon simulator is now available under an open source software license:
https://charon.sandia.gov

This is an exciting development in the world of TCAD simulation, to have an open source TCAD simulator targeted toward large simulation problems.

From their website:

Charon is an open-source semiconductor device modeling code, widely referred to as a TCAD (technology computer-aided design) code, developed at Sandia National Laboratories. It is written in C++ and relies on another Sandia open-source project, Trilinos, for supporting code, such as nonlinear and linear solvers, finite-element and finite-volume libraries, I/O, etc. In addition to running on most Linux-based computers Charon also supports simulation of extremely large problems on massively parallel computing systems that support the MPI standard.