3rd Party Liabililty Insurance
If something happens and the launch causes damages to any where on earth (not to Lauch Vehicle or to satellite), someone has to compensate the damages.
Normally if you're go up with commercial flight, Launch Provider will provide 3rd party liability insurance for you.
But if you're go on a governmental flight like OSSI, the launch provider will not cover the damages when something happens because of you. (but this rarely happens)
Why we need this?
Of course, to be responsible
If damages occurred, and this happens in countries that's not relevant to the launch, it became international issue. Then satellite owner's country and launcher owner's country need to solve the problem.
OSSI, as the satellite owner and lives in South Korea, needs to show to South Korean Government that OSSI is covered by 3rd party liability insurance to start space body registration
process in South Korea.