Would you be considered a participant in sin and held accountable before God if you, as an insurance company, paid out based on a (deceptive) oath sworn before a judge, because you conveyed or helped convey the idea to the person who swore it? And would it be different if you were the first to convey the idea to him? And would the money be guaranteed before God by whoever supported the idea of the oath to the person who swore it, or only by the swearer himself? And is the money taken by the other car owner unlawful if he colluded with them in lying? And do the police officer and the insurance employee sin if they collude? And does the one who swore the oath sin if he lied to you about settling the matter?

It does not appear that the oath taken by your friend is a Ghamus oath (a false oath taken intentionally to usurp a right); because the driver of the car was not mentioned.

Even if it were to be considered a Ghamus oath, the sin is lifted from one who is ignorant of the religious ruling.

However, one who is aware of the prohibition and assists in taking money undeservedly from the insurance company is sinful.

Commercial insurance is prohibited unless it is compulsory, in which case it is permissible to benefit from it only to the extent of what was paid.

If the amount paid by the insurance company is equal to your friend's contributions, then there is no liability.

If the money paid exceeds his contributions, then the liability rests solely upon him, not on the other instigators, and the money taken in this case is treated as stolen money.

If the owner of the other car colluded in lying, he is sinful, and what he took from the insurance company is forbidden for him. However, if he took it with the company's knowledge of the true situation, there is no blame upon him.