What are some alternatives?
When comparing Boxy SVG and Sketch, you can also consider the following products
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Affinity Designer - Professional creative software, exclusively for Mac.
Vectr - Free vector graphics editor. A simple yet powerful web and desktop cross-platform tool for everyone.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
Adobe Illustrator CC - Adobe Illustrator CC is a commercial vector graphics editor.
Adobe Illustrator - Adobe Illustrator is a vector graphics editor.