BetterFonts is a mod that allows Minecraft to use a TrueType or OpenType font rather than Minecraft's built-in font.

While using a mod depending on MalisisCore, I noticed that the UI used the built-in font from Minecraft, rather than the TrueType font used by the rest of the game with BetterFonts.

Unfortunately, MalisisCore guis don't use default Minecraft rendering, so I can't automatically use BetterFonts font directly.
I might allow the choice of default font for MalisisCore guis in the future, but it's not really high on the priority list.