Okay so I’ve finally looked into this and it makes some sense... and the headline (like the rest of the article), is WRONG.
Trump does NOT have to post a bond to appeal. What he has to do is post a bond to PREVENT ENFORCEMENT of the judgment while the appeal is pending:
CPLR 5519, Stay of Enforcement:
“(a) Stay without court order. Service upon the adverse party of a notice of appeal or an affidavit of intention to move for permission to appeal stays all proceedings to enforce the judgment or order appealed from pending the appeal or determination on the motion for permission to appeal where:
...
2. the judgment or order directs the payment of a sum of money, and an undertaking in that sum is given that if the judgment or order appealed from, or any part of it, is affirmed, or the appeal is dismissed, the appellant or moving party shall pay the amount directed to be paid by the judgment or order, or the part of it as to which the judgment or order is affirmed”
That's NYS. SCOTUS could grant a stay to prevent enforcement.