This is an effort to develop an user-friendly front-end to Giac (http://www-fourier.ujf-grenoble.fr/~parisse/giac.html), a CAS (Computer Algebra System) library by prof. Bernard Parisse, written in C++ and released under the GPL.
There is at least one more GUI to GIAC, by the same author, called Xcas (http://www-fourier.ujf-grenoble.fr/~parisse/giac.html). vaCAS attempts to have the same functionality that Xcas, and to extend it in the future.
One of the aims of vaCAS is to be available not only in the desktop PC, but also in handhelds and similar portable devices. vaCAS is part of a wider project called SDA (https://savannah.nongnu.org/projects/sda/), about a new concept of a scientific digital assistant, managed by J.Manrique (http://www.asturlinux.org/~jsmanrique/).
vaCAS does not exist yet, but I'm working on it. It will make use of the GTK+ library.