What do you exactly understand saying "open fonts"? I suppose you mean OpenType...
A problem is that one should have the same font installed on the two computers... That means, it should bear exactly the same name, too. And OTF fonts follow a different naming scheme than ordinary PS ones. And I must admit that I don't know if Mac OS 9 already works with such fonts, at least without ATM Deluxe 4.6.
But there's another possible solution that doesn't work with PS-flavoured OpenType fonts but with TrueType (at least in Word, but I suppose that should apply to other office apps like PowerPoint, too): just embed the TTF version (comes, AFAIK, with the Office package, have a look to a folder containing additional fonts on one of the installation CDs, and at least with Publisher but I have it somewhere on my system without Publisher, a program I'd never use, as it's far too poor for me (one can't even export to serious DTP or drawing programs, the only solution would consist in printing a PS or PDF file and import that one...). But that's yet another subject.
My suggestion is: try to find the TTF(s), embed it (or them if you use different styles and weights) and send those files to your friend. You may also create PDFs from your PowerPoint slides.
The other but most costly legal solution would consist of purchasing the OTF fonts twice, one licence for you, one for the Mac guy. If you use XP, you won't need ATM. Concerning Mac OS 9, I really don't know (but there should be a free ATM Light version for Mac, too).
Unfortunately, fonts are expensive (Adobe isn't worse than other foundries, and there are many places to buy). Some fonts come free with even cheap apps, but I don't know any Adobe program containing a free version of Franklin Gothic (BTW: there are several foundries that issued this font, at least Monotype and ITC; maybe this is also the possible source of the problem the different versions haven't exactly the same design either).
Hope that helps (BTW: your message is a bit OT, if you don't plan to use the FDK in order to create an OTF version of a PS font, which is very tricky and legally doubtful for a business use ;-)).
Christoph