The original translators released their work for free. The "repacker" merely compiled these free assets into a stable distribution format. However, you should avoid repacks that include trademarked assets (like real club logos) alongside the language files, as that enters grey territory.
The is legal under "Fair Use" and "Interoperability" provisions. Here is why:
If you're having trouble finding the right folder, let me know your operating system (Windows or Mac) and where you installed the game (e.g., Steam or Disk) so I can give you the exact path. Football Manager 2010 Language Pack No ... - Facebook