It is almost certainly one of three things:
Includes high-definition textures for roads, buildings, and vegetation, replacing the original low-resolution assets. gta sa remastered v6 hdr.7z
The mod itself is legal as it falls under derivative fair use. However, distributing the original gta_sa.exe or copyrighted assets (like music tracks or original character models) is illegal. A clean V6 pack should only include modified texture files, shaders, and scripts—not the full game. It is almost certainly one of three things: