For desktop apps only at the start. Will require a Verisign or other cert for distribution (no suprise there).
During the beta, all apps are free and can be self-signed.
Get the details here:
or java.sun.com :
Looks like the sign up process is quick. (Got approved for submissions to the store in about 5 min).
Too bad we have to wait until the end of the year for the JavaFX Authoring tool...