Because MathType was expensive (~$97 for a student license in 2013), many students used keygens. For versions 6.7 and earlier, those keygens worked fine.
Here is the story behind , a version that holds a nostalgic place in the timeline of scientific publishing. mathtype 6.8
Before MathType became a subscription service owned by WIRIS (and later, min Reform), it was developed by a company called Design Science , based in Long Beach, California. They created MathType as the professional version of Microsoft Equation Editor. For over a decade, version 6.x was their flagship product. Because MathType was expensive (~$97 for a student