Brandon answered that question, but I'll try to word it differently. The source code can be used as the basis for creating a ROM. We need someone to take the source code and compile a ROM that will actually be compatible with the Fascinate. There's a dude named Birdman that is supposedly working on it as we speak. He's put out some really cool stuff in the past, and I doubt this will be any different.
Yep.. A bit more detail for those interested.
You have two major parts.. The kernel, and the OS. For those of you familiar with MSDOS or early windows, the kernel was command.com. It's basically the brains of the OS, and what binds the lowest-level functions of the OS to the hardware level / drivers.
The OS is generally what people talk about when they throw around the term ROM. This is how the app drawer works, the default lock screen / home screens, basic menu systems, etc..The OS is basically HW independent. Similar to Windows, this is how you have the same Windows 7 on a Dell with an AMD quad-core, or a Sony with a Intel Core 2 Duo.
In order to make the OS work with the specific device, we need drivers. Drivers are OS (and obviously, HW specific). Windows 95 drivers don't (usually) work in Windows 7. Many Eclair (2.1) drivers need to be updated to work correctly with Froyo (2.2).
The kernel is also HW specific (in essence, board specific [cpu, memory, gpu, etc..]). While it doesn't need the full set of drivers (for instance, the kernel doesn't need WiFi drivers to boot up), there are many drivers it does need.
What Samsung has released today, and what everyone is talking about is the source code for Froyo (2.2) for the i9000. The source code for Froyo itself has been out for a quite some time now, so that is not a big deal. What is a big deal is that Samsung has obviously done all of the hardware and kernel level work for the i9000.
Our device is not the i9000, for those of you who are really out of the loop.
It is, however, in the same family, as the i9000 so instead of being ~50% of the way there (having generic Foryo source code), were now ~90% of the way there (having a lot of hardware specific work done). The problem is that we need to do the other 10% on our own (or wait until Samsung releases Froyo for the Fascinate).
There's a lot of work that needs to be done still, but this is a great leap in the right direction. I haven't worked with Birdman much, but from just his presence in the IRC channel for fascinate dev's I can tell he's very capable. As for his statement that Froyo would be ready in "hours", I think he may have been a bit excited and over-spoke.
My best guess, having worked directly with the guys who put Voodoo together, is that we're looking at maybe a week. I haven't looked at the source yet, but I will tonight. It's possible that 99% of the work is done. I know Samsung, so I doubt it, but you never know. I'll happily eat my words if Birdman releases tonight, but my gut instinct is that it's going to be a few days at least.
Hope that helps clear some stuff up.