There are several people still hacking away at Linux Gens, all more or less separately :/ I tried emailing some of them through Sourceforge, but never got any replies.
A fellow named wah_wah_1969 (who was actually the one to implement OpenGL) says he's working on a custom GUI that's done without any of that GTK mess. It might be some time before he has any results...
http://forums.gentoo.org/viewtopic-t-204287-postdays-0-postorder-asc-start-75.html
EDIT: I should add that personally, after using grrl for about 15 minutes I much prefer it over any other Linux Gens release. Being able to customize system keys and avoid the GUI entirely is a big plus, even just for regular playing. I think GTK is pretty ugly anyhow, both in terms of appearance and internals. So, thanks! :D
2nd EDIT: A feature I'd really like to see is the ability to bind a control to several keys in the config, i.e.
P1.Up=[8]
P1.Up=[5]
This would make it easier to add up+down and left+right input, among other things. I don't know how feasible that is, it's certainly not high-priority, but it would come in handy.