Unless you've been detained illegally in a black site prison, you probably know that Dungeons & Dragons Fourth Edition came out this month. Many folks are giving it a try and I've heard a lot of GMs lament the fact that there aren't any ready-made 4E settings available yet. Even WotC won't have their new Forgotten Realms campaign setting book out until August. This is the beauty of the Pirate's Guide to Freeport. It is a pure setting book that can be used with any fantasy RPG. It has no game stats at all, so you can just pick your game, add Freeport, and enjoy. If you are looking for a campaign setting for your new 4E game, you can start with Freeport right away.
The city can be used on its own or you can drop into any other campaign setting you like. You could even start a campaign in Freeport now, leave the rest of the world vague, and decide on the details of the larger campaign setting later. If you do want a full campaign setting right away, the Pirate's Guide includes an optional chapter on the World of Freeport. This details "the Continent" in some detail and provides a ready backdrop for all kinds of adventures.
To complement the Pirate's Guide, we have been doing a series of rules companions over the past year, which provide mechanical support for various game systems. We've done True20, d20, and Savage Worlds so far, with Castles & Crusades coming up next. We may do a Fourth Edition Freeport Companion if we can figure out how to do so under the terms of the new Game System License. In the interim, however, here are a few ideas on how to adapt Freeport to the 4E rules.
Levels: The Pirate's Guide notates each NPC as being an apprentice, journeyman, or master. This translates easily into 4E, since characters now have a level range of 1-30. Apprentice characters are heroic tier (1-10), journeymen are paragon tier (11-20), and masters are epic tier (21-30). Now Freeport is a lot grittier than the new D&D, so you might consider making max level 15. In that case, apprentices would be levels 1-5, journeymen level 6-10, and masters level 11-15.
Races: Dragonborn are a new race of draconic humanoids and they have not featured in Freeport products before. However, Freeport is known as the Crossroads of the World and all sorts of strange folk make their way to there. Adding a few dragonborn to the mix is easy enough, particularly as the PHB paints them as wanderers without a home. They may even have come from another plane of existence.
Another sort of new race is the eladrin. They are basically high elves, which makes them the best match for most of the elves that appear in Freeport. The PHB's elves would be the World of Freeport's wood elves and they'd mostly be found in Rolland.
Freeport does have gnomes, and although they are not an option in the PHB there are rules for them in the Monster Manual. Those looking to make villains out of gnomes need look no further than the World of Freeport's Autocracy of Iovan.
Classes: All the classes in the PHB can be found in Freeport. Pirates are best modeled by rogues, though fighters and rangers can also work pretty easily. Warlocks work well with the Lovecraftian elements of the Cit of Adventure. A warlock with a star pact with the Unspeakable One would make a quite suitable cultist.
Points of Light: WotC is pushing the idea of "points of light" campaign settings. The basic idea is similar to that of Warhammer's Old World. There are villages, towns and cities that are pockets of civilization but between them are large areas of untamed wilderness that are by no means safe. At Green Ronin we like to offer many different models for campaign play, but if points of light is your thing the Ivory Ports is probably the best area of the World of Freeport for that. A border area of Hexworth could also work, with adventures focused in the Bone Lands.
These are just a few ideas on how to use Freeport with 4th edition. If you have more, come on over to the Campaign Settings message board on GreenRonin.com and share them with your fellow gamers.