I've found a font that only comes in Linux and Windows versions, is there any way to install it on Mac OS X using either of these versions?
EDIT: I am open to format converting, but preferably with free software.
AFAICT, .fon represents a Windows bitmap font. For the most part, pure bitmap fonts aren't supported in Mac OS X, so you won't really be able to easily convert this to a Mac version that is usable in most native Mac OS X environments. I say "for the most part", because the only part of Mac OS that may have supported explicit bitmaps was QuickDraw, which has been deprecated for quite some time.
The Mac OS X font architecture requires that fonts be vector-based. So, for instance, you might be able to convert the FON bitmaps into a traditional Mac font suitcase that would hold several
Now, given enough time and the right software, it would be possible to trace the bitmaps to create a vector version, though we'd be talking hours to days of time invested.
I'm not as sure about things under the X11 environment, as it may support the X11 form of bitmap fonts, though these won't be available to other native OS X apps.
If you're looking for a programming font, I use my own tweaked version of ProFont:
This version of ProFont looks best at 9pt, and IMO, doesn't work as well at larger sizes. (I'm pretty sure that could be improved by tweaking the hinting in the font, but I haven't even begun to understand how TrueType hinting works).
Mac OS only accepts TrueType fonts (.ttf) or OpenType fonts (.otf) but not Generic fonts (.fon). However, there are online converters available to convert .fon to .ttf or .otf. An example would be this one: http://files-conversion.com/font-converter.php