Not at all. There is even evidence in the FSF documentation somewhere exactly
about this point and they vehemently disagree with any attitude like that. We
all know very well the situation of Emacs, Xemacs, and various other forks.
The
FSF is not the law. I suggest you look up Trademark Law to realize why
you are wrong, and why you are subject to a lawsuit for knowingly
creating a product that is infringing on an already existing
trademark(Regeristered or Unregeristered would make a small, but only
small, difference in this case), and can easily be confused as such.
In fact the case against forcing you to change it is rather strong
because not only is your product nearly identical in name, it is nearly
identical in function and can be easily confused with the original.
Standard disclaimer of I am not a lawyer of course applies.
Seablade