Bowser was ordered by a court to pay $4.5m restitution to Nintendo after pleading guilty to two criminal charges (the specific charges he pled guilty to are unclear, but he was charged with fraud, DMCA circumvention, conspiracy and others). Separately, Nintendo brought a civil suit against him, and the court entered a judgement in favour of Nintendo (following a consent agreement) for $10m.
These are debts that Bowser owes, and whether certain of his income is taxable or not is not relevant to whether it is available to pay those debts. A "private settlement" would still be very unlikely to contain some specific list of sources of income that were affected by the debt.
Should he decide to adopt your (very strange, especially for a former lawyer) stance in your grandparent comment that non-taxable income would somehow be, by virtue of its tax treatment, shielded from these debts, he would simply find himself back in court for failing to pay.