YoYo Games highly recommends moving to the current version of GameMaker for several reasons:
Since GameMaker 8.1 is considered "abandonware" and lacks support for modern operating systems like Windows 10/11, it is highly recommended to move to current versions: Legacy GM GM 8.1 Activation question license key for game maker 81 pro link
: Official sales ended in 2015. There is no legitimate storefront where you can buy a new Pro key for this specific version. YoYo Games highly recommends moving to the current