As a developer, you can support FontSmoother in two ways. First, you can do nothing. In that case, your users should be able to use FontSmoother in your applications via Fonts4OS5. I do recommend, however, that for optimal performance with exact-spacing kerned fonts you lay out text in your application in kCoordinatesNative coordinate mode. Using a 16-bit display mode will result in better quality than using an 8-bit mode.
The second option is to use FontSmoother fonts as custom fonts in your application via FntDefineFont(). A FontSmoother antialiased font package typically contains an 'nfnt' or 'NFNT' or 'afnx' font resource which is an ordinary non-antialiased font: I will call this "the Basic Font". This font, however, contains the information on how to find the antialiased bitmaps and the database containing them. All you need to do to use the antialiased font is call FntDefineFont() with a pointer to the Basic Font and make sure that the user has hotsync'ed the database that contains the antialiased bitmaps.
If your application already supports custom fonts, all this should be very easy. In fact, if your application accepts FontHack-style fonts in databases of type 'FONT' and creator id 'FONT', then you do not need to do anything--the user can just hotsync fonts in the FontHack_fonts directory of the FontSmoother distribution if you use 'NFNT'-format fonts, i.e., FontTypeV1 ones or fonts in the MobiPocket_fonts if you use 'nfnt'-format fonts, i.e., the new FontTypeV2 fonts that came in with OS 5.
If your application does not support custom fonts, the optimal option is to scan through 'FONT'/'FONT' databases and use the ones you find there. If you draw text directly on screen, you should probably use MobiPocket-style databases with 'nfnt' (FontTypeV2) fonts. Each record in a 'FONT'/'FONT' database is a non-antialiased font. You can check if it's a FontTypeV2 font by checking if the first byte of the record has the 0x20 bit set. A bonus of doing things this way is that you will also end up support non-antialiased custom fonts in MobiPocket-style packages. Such fonts can be generated from other font formats via Font Collector (search the web for it), either by you or the end user.
Alternately, and more simply, you may wish to build an antialiased font right into your application. A good way to do this is to have the Basic Font reside in an 'nfnt' resource inside your application, and then just call FntDefineFont(). The user who wants antialiased rendering then needs to be instructed to separately hotsync the database containing the antialiased bitmap and related resources. You can generate a Basic Font plus antialiased bitmap pair by starting with a MobiPocket-style FontSmoother font (e.g., one of the ones in the MobiPocket_fonts directory of the FontSmoother distribution). Such a font contains two files that need to be hotsync'ed: a .pdb file and a .pdb-resource.prc file. The .pdb-resource.prc contains all the antialiasing data for all the fonts in the .pdb file, while the .pdb file contains all the corresponding Basic Fonts. You can generate such pairs from TrueType or Type 1 fonts via PalmFontConv or EasyConvert. Simply extract the Basic Font(s) from the .pdb file and use them in your program and ask a user who wants antialiased fonts to hotsync the other file. You can extract records from a .pdb file via the par swiss-army knife utility: just run par x database.pdb. Doing this by this route should let you build an antialiased font into your application in only a few minutes of coding type to include the requisite FntDefineFont() calls.
More complicated options are available. Since the source code PalmFontConv (search the web) is available, you may be able to figure things out for yourself. If not, contact the fontSmoother developer.
You are free to bundle an unregistered copy of FontSmoother with your application if you include the entire FontSmoother distribution and point the user to a page where it is sold. Other licensing options are available--just ask me.
You can include the fonts included with FontSmoother in your applications provided that you abide by their individual licenses in the *-license.txt files in the FontSmoother distribution.