Essentially the rules are this:
• If 18 years old or younger on the June 5 preceding the player's original signing date, the player is subject to selection at the fifth Rule 5 Draft following the player's original contract;
• If 19 years old or older on the June 5 preceding the player's original signing date, the player is subject to selection at the fourth Rule 5 Draft following the player's original contract;
Morlan was 18 when he signed in mid-June, 2004. Meaning he passed drafts in 2004, 2005, 2006, 2007, and is now eligible for the 2008 Rule 5 draft. The Rays can no longer add non-free agents/traded players to the 40 man, so unless he's traded, he's going to be selectable. The good news is, he's unlikely to stick on a roster for the entire season. The bad news is: he's apparently not what we were hoping for, despite decent numbers last season.
Edit: Unless there's some injury bypass the Rays can press for, since Morlan did miss time with a shoulder injury this year.
There's not.
Others who appear eligible:
Ryan Royster
Chris Nowak
Matt Spring
Wood Fines
Wade Townsend
Chris Mason
Mike Wlodarczyk