Getting windbg without the whole WDK?

Actually, Microsoft has now made the Debugging Tools downloadable separately from the SDK. Look for the section "Standalone Debugging Tools for Windows (WinDbg)" about mid-page:

• for Windows 8.1

• for Windows 10

Officially, you can't. But someone's been extracting them for your convenience and hosting them.

Note: You can get the older releases on the official site, but the latest ones are part of the WDK.