They dual licensed under BSD and GPLv2: https://github.com/facebook/zstd/issues/335#issuecomment-323606863 https://github.com/facebook/zstd/issues/335#issuecomm

They dual licensed under BSD and GPLv2: https://github.com/facebook/zstd/issues/335#issuecomment-323606863 https://github.com/facebook/zstd/issues/335#issuecomment-323... I expect they did a thorough analysis to work out if any of it was either already patented, or patentable. That doesn't mean they don't have patents though.