OK, I found what I think is my final answer. It's on the IRS website. My father's case *is* self-employment income. This used to be on IRS publication 533, but now it's here:
<a href="
http://www.irs.gov/instructions/i1040sse/ar02.html" rel="nofollow" target="_blank">
www.irs.gov/instructions/i1040sse/ar02.html</a>
["Other Income and Losses Included in Net Earnings From Self-Employment"
6. Amounts received by current or former self-employed insurance agents and salespersons that are:
- Paid after retirement but figured as a percentage of commissions received from the paying company before retirement,
- Renewal commissions, or
- Deferred commissions paid after retirement for sales made before retirement.
However, certain termination payments received by former insurance salespersons are not included in net earnings from self-employment (as explained in item 10 under Income and Losses Not Included in Net Earnings From Self-Employment).
]