I have recently updated my FontEdit app to support Linux PSF fonts as well as my own format.
You can load either my format bitmap ('Font'), or either version of the Linux PSF font formats (version 1 or 2), modify the characters, then save as any of the three formats.
This allows you to open one format and save as another.
Why? Well, if you are creating your boot/loader code on a modern machine, you no longer have the ability to write a character to the video hardware as with legacy machines. You actually have to write the character to the screen a pixel at a time.
These pixels are usually stored as bitmaps. It would be a tedious task to create these bitmaps by hand, so that is why I created this application. It makes it quite easy, and now you can load any of the Linux PSF fonts.