As always, your best and most definitive course of action is to seek actual legal counsel with experience in copyright law. I'm not a lawyer and, as such, the following should be viewed only as my opinion and not legal advice.

The key phrase in the PDF that MrChrister linked to is:

if the parties expressly agree in a written instrument signed by them that the work shall be considered a work made for hire.

My understanding is that unless there is clear verbiage in writing regarding a work for hire and the ownership of the work, anything created is automatically considered the intellectual property of the creator of the work, not the commissioner of the work. The process is automatic and the act of creation itself is sufficient to ensure intellectual property rights, meaning that applying the actual © symbol is largely redundant and serves more as a deterrent rather than a legally-binding action.

For this particular case, if there is concern, again, my advice would be to contact a lawyer to clear up any lingering issues or doubts. If the situation is bad enough and has not actually been handled through court, the first developer could come back at a later date. (While I seriously doubt the veracity of his case, the person currently claiming to own 80% of Facebook would be a good example of this). I'd suggest legally checking into it now, even if it's more of a hassle and more expensive. The peace of mind may be worth it.

As an aside, it's situations like this that make it necessary to always have a written contract. Good contracts should clearly define ownership, responsibility, tasks to be performed, and should provide clear steps of action to be taken if one or both parties do not fulfill their obligations. If you're working without a contract, you're working without a net. It might not be today, but one day you'll fall.

As always, your best and most definitive course of action is to seek actual legal counsel with experience in copyright law. I'm not a lawyer and, as such, the following should be viewed only as my opinion and not legal advice.

The key phrase in the PDF that MrChrister linked to is:

if the parties expressly agree in a written instrument signed by them that the work shall be considered a work made for hire.

My understanding is that unless there is clear verbiage in writing regarding a work for hire and the ownership of the work, anything created is automatically considered the intellectual property of the creator of the work, not the commissioner of the work. The process is automatic and the act of creation itself is sufficient to ensure intellectual property rights, meaning that applying the actual © symbol is largely redundant and serves more as a deterrent rather than a legally-binding action.

For this particular case, if there is concern and there was no written contract, again, my advice would be to contact a lawyer to clear up any lingering issues or doubts. If the situation is bad enough and has not actually been handled through court, the first developer could come back at a later date. (While I seriously doubt the veracity of his case, the person currently claiming to own 80% of Facebook would be a good example of this). I'd suggest legally checking into it now, even if it's more of a hassle and more expensive. The peace of mind may be worth it.

As an aside, it's situations like this that make it necessary to always have a written contract. Good contracts should clearly define ownership, responsibility, tasks to be performed, and should provide clear steps of action to be taken if one or both parties do not fulfill their obligations. If you're working without a contract, you're working without a net. It might not be today, but one day you'll fall.