As others have mentioned, Buck was open-sourced before Bazel but obviously inspired by Blaze. There's also Please, which we wrote as a Buck replacement before

As others have mentioned, Buck was open-sourced before Bazel but obviously inspired by Blaze. There's also Please, which we wrote as a Buck replacement before Bazel was open sourced: https://github.com/thought-machine/please https://github.com/thought-machine/please (disclaimer: I wrote most of it...)