Question: Does anyone know of any opensource tool for creating dynamic organization chart in flex by reading values from database

Answer: 
Have a look at KapLab (<http://lab.kapit.fr>)

They have free data vizualisation components. I think you might be interested by the Visualizer component. 

It's not open-source though, but you can get the source code if you buy a licence.

(If you need more info, you can still contact me because I'm working closely with them)
Maybe The Flare library would suit your needs , I am starting to use it. Looks kinda funky

<http://flare.prefuse.org/>