Open source design collaboration with Penpot: 
When a team of designers works together on a project, one of the most important goals is consistency. Whether you need a consistent look because of a corporate identity or just for visual cohesion, the look and layout of pages and screens must be reasonably similar within any given project. It’s hard enough to do this as a solo artist, and it gets more complex with added contributors. It becomes a monumental task when several mock-ups from a design team must be approved by a client, signed off by an accessibility expert, and then translated by a team of programmers.
read more: Opensource.com sethkenlon
Supporting Open Source.
Have you tried: Diving with Sharks?