sp_WhoIsActive is a comprehensive activity monitoring stored procedure that works for all versions of SQL Server from 2005 through 2019 and Azure SQL DB.
sp_WhoIsActive is now officially versioned and maintained here on GitHub.
The license is now GPLv3.
Documentation is also available at http://whoisactive.com/docs
If you have enhancements, please consider a PR instead of a fork. I would like to continue to maintain this project for the community.