The download page says this about Seam 3:
NOTE: This build is currently not working correctly due to recent changes to CDI and Weld. Consequently, I haven't invested any time in doing much with it. Any ideas when the build might work correctly?
The individual modules will become buildable as they get more attention. For example, remoting can be built now and is actually getting closer to some kind of preview release. My best suggestion is to keep an eye on http://in.relation.to, I'm sure that each module developer will post there once they have a release.