GTK-server is a free, open-source project, which offers a stream-oriented interface to the GTK libraries, enabling access to graphical user interfaces for shell scripts and interpreted programming languages using either GTK 1.x or 2.x. It was inspired by Sun's DeskTop KornShell (dtksh) of the Common Desktop Environment (CDE) for Unix.'
Judging from the examples, the API one gets with GTK-server is at about the same level as one would get by using SWIG on the GTK C headers, i.e., it's a lower level interface than Tk. Might in that respect rather be comparable to ffidl and TWAPI.
escargo 2008-04-21: It depends on whether you want to compare the level of interface or the mechanism of the interface. I suppose one could write some wrappers with Snit to provide a higher-level of interface.
FF 2008-04-21: wrappers to GTK+ in Snit, that would be awesome! it'd be like all the beauty of GTK+ plus all the good flavour of Tk... yum yum!
escargo: I am not sure what it might buy you that gnocl would not. One hopes a direct binding might operate better than a stream binding. It would be interesting to test the two alternatives together.