There is a hard dependency on gtk which is not necessary. The ebuild for libdv should recognize the USE flag gtk/-gtk and do the appropriate thing. From the ./configure --help: --disable-gtk disable use of gtk for display [If you want a freevo/transcode box without X (but with fbcon and sdl), disabling this is necessary.]
Sorry, has been fixed in newer ebuild. libdv-0.99-r1.ebuild is correct. Seems like this should go to stable.
New patch is in portage. It will go stable after I get some confirmation that it is working properly, please try it and comment on bug #27139 with your experiences.