What keeps you from beginning your Start Up?
chriskelley: For me, it's freedom.   And only he can give that to himself.  I would say your best option is to support his decision, but give him a big welcoming door to walk back in if his startup doesn't work out.   Sometimes people with the drive to do things on their own need to try it first, and maybe it won't work out for him.  Then he will come back to your company with that much more experience, plus he will be more invested in your company emotionally as you supported him along the way.It's hard to lose good people, but even harder to see somebody leave their dreams on the table.