Visual Studio Code is not Open Source

Visual Studio Code is open source in the same sense as Google Chrome, that is to say not.

If you don't believe me, open Visual Studio Code, press F1, type "license" and run the "Help: View License" command. This will take you to https://code.visualstudio.com/license where it says that you may not

share, publish, rent or lease the software

or

reverse engineer, decompile or disassemble the software, or otherwise attempt to derive the source code for the software except and solely to the extent required by third party licensing terms governing use of certain open source components that may be included in the software;

This the license of the actual program you are running on your computer. Do not confuse it with the license specified in the Code - OSS repository https://github.com/microsoft/vscode.

Code - OSS is to Visual Studio Code as Chromium is to Chrome.

A summary of the proprietary parts which go into Visual Studio Code is available at https://github.com/microsoft/vscode/wiki/Differences-between-the-repository-and-Visual-Studio-Code#what-goes-where. Importantly the parts responsible for Visual Studio Marketplace Integration and Telemetry, Surveys, Crash Reporting are proprietary.