wxPython Licence vs GPL

[bonono at gmail.com]

Steve Holden wrote:
> Whether or not some fragments of code remain unchanged at the end of
> your project, if you start out with a piece of source code lifted from
> wxPython then what you have created is definitely a "derivative work"
> and, as such, you must take into account the wxPython license in your
> licensing of the derivative work.
>
Is that true ? What if I remove/replace the copyright doubtful portion
with another implementation ? I believe this happens all the time in
commerical software sue too.