[nimih]

My understand of Buck (and Pants) is that they are the result of ex-Google employees going to other companies (resp. Facebook, Twitter), realizing that Blaze was more or less the Right Way to do a build system (at least for their set of circumstances), and then being forced to re-implement the ideas from scratch (edit: or memory, or exfiltrated docs/code) because Blaze was not open source. Reusing extant software is great, but it requires that software to be available to you in the first place.

[plorkyeran]

Bazel is basically current Google employees doing the same thing due to how tightly Blaze is tied to Google infrastructure. Any open source projects or things that may one day be a separate business unit under alphabet rather than part of Google can't use Blaze, so they set out to make a version of Blaze that they can use.

[shereadsthenews]

“Reimplementation from scratch” seems like a generous description of Buck. It was initially so like Blaze that I always assumed a xoogler exfiltrated at least the documentation of Blaze.

[nimih]

I really can't speak to that in any way, I was just trying to answer the OP's question as to why there are a number of--on face very similar--Bazel-style build systems. It certainly seems like a fair assumption, though.

[tex0]

Buck definitely looks familiar, having worked with e.g. bazel.

[puzzle]

I remember that being a former Google intern.