In the niche world of semiconductor physics and organic electronics (OLEDs, solar cells, and perovskites), by Fluxim AG is the gold standard. This simulation software allows researchers to simulate layer stacks, optical outcoupling, and electrical behavior without building expensive physical prototypes.
Most "cracks" available on torrent sites or file-hosting services (Uploaded, Rapidgator) claiming to be are repackaged versions of older, unstable builds (v 3.5 or 4.0) dressed up as the latest version.