installed from pkg(8) into a KDE workspace also installed w/ pkg(8), so I'd say
all defaults to compile the port applied, and all automagic dependencies should be fullfilled.

Misbehaviour:
1. clicking a menu item in the main menu -> it pops up very shortly, then hides;
   no menu item of the submenu can be be choosen
2. clicking the down-arrow beneath the ISP selection box has no effect
3. the selection box/field to select (or write the name of?) the ISP does not
   receive the input focus. Thus it is neither possible to write s/th in it, nor
   to select one from the list, since the list does not open (see previous)
4. in general, it's visual appearance is too small
   - on 96 dpi: at the edge to be readable
   - on a high DPI display: totally unreadable

It's hard for me to say which is a problem of:
the app itself/Gtk toolkit/port configuration
So this is all guessing:
This last bug might be a general problem of the toolkit choosen.
From 1. follows there is is no general problem to receive input, at least mouse.
The startup warning (see subject) might also be related to the sizing issue?  At least the "Sans" font should be available.  Maybe the program misses to call some neccessary toolkit init to get all the right settings for fonts, display etc.pp.?

This program looks so promising and I do not care that it's visual appearance is different from what I use (KDE/Qt) (It looks very clumsy and Motif-like, though... who cares).  But I never encountered problems like those described with other Gtk apps.  Maybe there's some library missing in the port's configuration and/or the program's init routine?