For a limited time, Yoyo games have made Game Maker: studio Standard free, you can read about it over here.

Instructions:

• Download GM:S from here.
• Install but don’t choose a license just yet.
• Go to the GM:S icon in your system tray and switch to beta channel and update
• Restart GM:S
• There should be three license options, choose the middle one.
• After following it’s instructions you should have GM:S, enjoy!