Correction - you can start JBoss AS 5.0.0.GA - you even posted the evidence that it started. The problem is that Eclipse is not recognizing that it started, which makes it an Eclipse problem.
Do you have JBoss Tools installed into Eclipse? If not, please do so, it appears to be able to handle JBoss AS 5.0.0.GA correctly (reports it as "Started").
If you do not have JBoss Tools installed, then you should ask this question in an Eclipse forum.