From the Fink FAQ:
Q8.11: I installed Apple’s X11 in Panther but Fink keeps asking to install xfree86.
In addition to the FAQ answer above, be sure to look for all other xfree packages! I used to have xfree86-rootless installed instead of the standard xfree86-base.
[dyn-002:/sw/etc/apt] sean% sudo dpkg -l | egrep -i xfree
iU xfree86-rootle 4.2.1.1-16 XFree86 libraries, utilities, clients and da
ii xfree86-rootle 4.2.1.1-16 XFree86 libraries, utilities, clients and da
After adding the remaining xfree-rootless packages to the removal list, Fink finally stopped complaining about needing xfree86.