MKVToolNix is actually a well-known open-source software suite used for creating, altering, and inspecting Matroska (MKV) files. Since the official software is , there is no need for a "crack" or product key.
The text you've provided appears to be a link for a "cracked" or pirated version of , rather than a scholarly or professional paper.
: These "cracks" are common delivery methods for trojans, ransomware, and spyware.