Name: ipe
Site: http://ipe.otfried.org/
Why? :
Ipe - extensible drawing editor is a toole, like inkscape, for drawing vector graphics. However, where inkscape is very free hand, IPE makes sure to constrain you to grids or angles. This makes it ideal for drawing physichs and math figures. It creates figures nearly on level with programatic figure programs (tikz, matplotlib or something like that), however more user friendly than those)
Copyright: Gnu General Public License
tar ball: https://dl.bintray.com/otfried/generic/ipe/7.2/ipe-7.2.7-src.tar.g
He doesn't really use git that much, but there is a github page: https://github.com/otfried/ipe
Is in the AUR (https://aur.archlinux.org/packages/ipe)
Is in open Suse (https://software.opensuse.org/search?utf8=%E2%9C%93&q=ipe&search_devel=false&search_unsupported=false&baseproject=openSUSE%3ALeap%3A42.2)
in ubuntu 16.10 (http://packages.ubuntu.com/search?keywords=ipe&searchon=names&suite=yakkety§ion=all)
is in geentoo (https://packages.gentoo.org/packages/media-gfx/ipe)