Polygon has accused Matter Labs, the developers of zkSync, of copying code from its Plonky2 library without attribution and making false claims about their own work. Plonky2 and Starky are two zero-knowledge proof systems developed by Polygon that are necessary for building a ZK L2. The libraries were open-sourced under a permissive MIT/Apache license as part of Polygon's plan to be net contributors to the ecosystem. Polygon argues that exploiting open-source code without attribution goes against the ethos of the community and harms the ecosystem.