Penpot

Penpot is an open-source design and collaboration platform for interfaces and other visual work. Its website explains vector-design tools, prototypes, team workflows, and the available hosted or self-managed options.

Teams can inspect the product's features and choose a setup appropriate to their collaboration needs. Hosting, account access, extensions, and support can have separate terms. A prototype or design file is distinct from a fully implemented application and still needs engineering and behavior checks when translated into a product.