[paulajohnson]

That doesn't make sense. As soon as the developer wrote the code (I.e. fixed it in tangible form) he had copyright in it. Copyright cannot be transferred except by a specific written transfer, which doesn't exist in this case.

[yborg]

Not really enough information to go on here. If there was something in the agreement prohibiting "derivative works" it would seem that TD Ameritrade could prevent the developer from making use of the service-derived product, but as you say, this shouldn't invalidate the developer's copyright or give ownership to TDA. The actual EULA text would have been useful here.

[SamReidHughes]

Doing it electronically counts as "written" under law. Correct me if I misunderstand this -- there is a specific law about that, the specifics might not apply here though.