If you're interest to learn what PowerShell Open Source, check links below:
https://github.com/PowerShell/PowerShell
https://github.com/PowerShell/PowerShell/tree/master/docs/learning-powershell
https://github.com/PowerShell/PowerShell/blob/master/docs/installation/windows.md
Now, this is all about PowerShell 6.0 (not Windows PowerShell) but there's a version for Windows available. This open source version can be installed along side Windows PowerShell on Windows 8 or greater. Also, you can contribute in providing feedback enhancements and bug fixes as is all available in GIthub. You just need an email account and start contributing.
Now, because this version of PowerShell, you install it on Linux and Mac OS. So, for creating, and executing PowerShell scripts, you can use Visual Studio Code editor in non-Windows OS's. Please check my 3 part blog series on how to execute PowerShell in VS Code in Linux and Windows:
I hope you'll find the blog interesting as I'm showing how to customize VS Code for working with PowerShell.
If you need more information about VS Code, check this link:
https://code.visualstudio.com/docs#vscode
