Open Source C++ Vector Graphics Software for Mac

Synfig is a powerful, industrial-strength vector-based 2D animation software package, designed from the ground-up for producing feature-film quality 2D animation with fewer people and resources.

See https://www.openorienteering.org/apps/mapper/

Sailcut CAD is a sail design and plotting software. It allows you to design and visualise your own sail and compute the accurate development of all panels in flat sheets.

Knotter is a highly configurable interlace designer. Interlace patterns are a kind of design historically used as a decorations in many places and by different cultures, some examples are Celtic knotworks and Islamic interlaces. Knotter aims to allow its user to design such patterns in an intuitive way and to provide easy ways to integrate the result in external general-purpose graphic software. For this purpose, designs created within Knotter can be save in a custom human-readable format and exported as Scalable Vector Graphics and in a wide number of raster image formats.