This page only contains a version of the PCKIMMO user interface. You should try out the English language files (englex.tak), which are quite large and can analyze most of your standard English words. You can also enable the tree representation if you like.
Note that there is also a "generate" mode which allows you to enter root+morpheme and lets PCKIMMO come up with a surface form. Eg. you could enter "fox+s" (without the quotes) and PCKIMMO will give you the correct surface form.