The FREE Swordfish Express app is still here:
http://buyolympia.com/software/products/swordfishexpress/v1/

Endicia may be just the ticket for commercial applications, but the stamp feedstock is prohibitively expensive for most household mailing needs. It adds about $0.105 to the cost of postage, or, as little as 7 cents additional if you buy 2000 labels at once. If the USPS added 10 cents to the First Class rate, the public would have a collective conniption. Prospective buyers should also know that Endicia is the only supplier for the stamp feedstock for the LabelWriter Turbo label printers. This monopoly (synonym for price-gouging) is said to "protect" the user from illegally printing unauthorized stamps, but it is not clear just how such a risk could arise, or, who would be liable for such unauthorized postage. Add to this the fallibility of the LabelWriter printer (400 Turbo), which occasionally allows a jam-up with the sticky side of the label rolling around the platen, and you have mega-potential for additional expense. The software warns you that you have to have enough labels on the roll to complete a multiple-stamp printing, but it doesn't tell you what happens when the first (or subsequent) label in the queue jams the printer. Simply put, you lose (at least part of) the value of your print order. For example, if you wanted to print 100 First Class stamps and the first one jammed, Endicia charges you for the full 100, a loss of $44 at the current rate. This is truly unnecessary when modern print drivers can "know" the hardware status of the printer in real time and prevent excessive loss from inevitable hardware failures. The final straw on the dromedary's back is that the user cannot specify a particular postage value for an individual stamp but must choose from a very limited drop-down menu--UNLESS (you guessed it) you purchase an Endicia postal scale (a $106 value at this writing ;) that transmits the stamp value back to your computer so that you can be correct to the penny! There are workarounds, of course, such as printing one stamp at a time, or going to the Post Office. One final caution if you decide not to go back to the old-fashioned lick-em-'n-stick-em, save the last 2 or 3 passwords that you have used on your Endicia account so you can log in successfully even if their last system restoration has lost track of your most recent password.

v1.3 (free), which is compatible with Leopard, can be downloaded from:
http://www.buyolympia.com/software/products/swordfishexpress/v1/.
In fact, I just used it to print a Priority Mail label.

How is this different from Click 'n Pay directly on the USPS's website?

Wonderful application!!! It's very useful if you ship alot stuff like me. With this, it's so convenient. Thank you!! It makes my life much much easier.