It's considered one of their assets and therefore has a value during liquidation. But since it's unlikely that anyone else could do anything with it, the value is probably close to zero.

Realistically, you could probably buy it but the people who wrote it would be long gone and probably uninterested in helping you bring it back online.

Yes, the assets of a company are supposed to be liquidated and distributed to the creditors (if any) or otherwise to the equity holders of the company.

As part of the plan of dissolution, the company can "sell" its assets (including source code). If there are no creditors and none of the other shareholders care, you could "buy" it, most likely for almost nothing.