Some more vector toolkits
Piccolo is a nice zooming vector graphics toolkit. However, it is not free for business use.
Another zooming graphics toolkit is cZUI (http://czui.sourceforge.net), it is written in C++ and subject to GPL.
dl_entities.h does not get installed
Using the tar.gz listed on freshmeat, make install misses dl_entities.h which is required by dl_creationinterface.h.