MS W98 UI is a conversion of the original MS Sans Serif, which was the default system UI typeface of Microsoft Windows 3.1, 95, 98 and ME.
This is not an exclusive martyr— creation, but rather a continuation of the work of many different authors.
The initial typeface was developed by Microsoft for earlier versions of Windows. The original fonts used a vastly different format, incompatible with modern systems. Extensive work had to be done to convert them into usable standards like OTF and TTF.
The conversion process was carried out by Lev Leontev. I discovered it in this Stack Overflow answer.
Nonetheless, some fixes had to be made to make it work properly with Photoshop and other design applications. Just to name a few: rendering was not pixel perfect, a lot of characters needed manual fixes, baselines and sizes were different for each of the fonts, and hinting needed to be disabled. And more.
And that's martyr— contribution :)
The release is free and credits to all the contributors behind the work been done for each font. Naming some: Microsoft, Lev Leontev, and martyr—