There are two major versions of BuildStream currently supported.
Apache BuildStream 2 is the latest stable version. We recommend that all new projects use Apache BuildStream 2.
BuildStream 1 is the "classic taste" version, stable and supported since 2018. No new feature development is planned for BuildStream 1.
If you want to build a specific project, check its project.conf file for the min-version. If the setting is 2.0 or above you need BuildStream 2, if the setting is not present then you need BuildStream 1.
Note that a porting guide is available to help you migrate projects from BuildStream 1 to BuildStream 2.
You can also browse documentation for future unreleased versions from the master branch here.