Unaffiliated with, but an extremely pleased user of http://www.youneedabudget.com.
accounting is more a business thing. all accounts needs to be balanced ie you always needs to have zero.
Is this incorrect?
However, in "normal" double-entry accounting, you would not have assets and liabilities on the same side of the balance sheet, and the way YNAB does this leads to some strange behavior. For example, if your net wealth (assets and liabilities) is negative, you need a negative budget ("pre-YNAB debt"). So now you have in your budget both money you plan to spend on actual expenses, and debt.
You could, in principle, design a YNAB-like double-entry accounting system where your assets balance against equity and debt, and where the money that is "available to budget" matches the actual money you have available, regardless of whether that money originates from equity or debt. That would be closer to the normal understanding of double-entry accounting.