Question: Since Yosemite, the green button in the upper left corner on each window activates the fullscreen mode. By holding the `alt`/`⌥ Option` key, it works as before (Mavericks). Is there any possibility (Terminal?) to change this behaviour back to "normal"? For example: holding `alt` for fullscreen mode?

**Update**

[You can change the behaviour back to "normal" with BetterTouchTool.](https://apple.stackexchange.com/a/157274/41559)

Answer: 
I use `alt` + `shift` + the green button. This reflects the Windows maximize button behaviour.
According to this [page](http://osxdaily.com/2015/03/11/change-the-green-button-maximize-behavior-in-os-x-yosemite-with-bettertouchtool/) you can achieve this using BetterTouchTool

1. Download [BetterTouchTool](http://www.boastr.net/) here
2. Open BetterTouchTool and grant access to “Accessibility” when requested (this will open System Preferences > Security > Privacy > Accessibility)
3. Allow BetterTouchTool access in OS X Preferences
4. Back in BetterTouchTool, click on the “Other” tab in the upper right of the app
5. Select “Global” from the left side options
6. Near the bottom, click on “Configure New Trigger”
7. In the “Trigger” pulldown menu, choose “Leftclick Green Window Button”
8. In the “Predefined Action” menu, choose “Zoom Window Below Cursor”
9. Flip back to the OS X Finder (or another open app) and click the green button, it should now simply maximize the window rather than send it into Full Screen Mode (even if the icon changes to fullscreen when the mouse hovers).
10. Close BetterTouchTool preferences pane (Red Window Button)

The changes will stay in effect as long as you have BetterTouchTool runs in background (its icon should appear in the menu bar, and that it is configured this way.