Well the article you reference certainly seems to answer the question.
I spent a half hour on the phone with the IRS today who told me that my client could contribute, and he referenced the "over 21, made $600, etc." When I said I believed that referred to an employer sponsored plan, he said he didn't want to argue semantics.
That's the expert.
If a statutory employee received W-2 from her employer and those income is recorded on her Schedule C, would those Schedule C income be considered self-employment earnings for making maximum contribution to a SEP IRA, and the plan was set up under the employee's name?