Quite likely he is alive. Why?
(1) Al Qaeda usually did announce the death of leaders within a few days. With each day without hearing from them, the news gets less likely.
(2) Usually, after the death of eminent Al Qaeda leaders the number of E-mail within that community has increased sizably. The services monitoring these E-mails do not see an increase this time.

Who is responsible for the rumour?
Surely not the Bush government as some narrow-minded Bushists (whatever happens lets talk about Bush) speculated here and in another thread.
(1) The way via a French provincial newspaper is not likely for a Bush plot.
(2) These news do not help Bush in the midterm-elections for they only focus one more the attention of the people to his stupid policy of invading Iraq instead of making a thorough job in Afghanistan.
So who did start the rumour (without forgetting that sometimes rumours start without anyone plotting)?
(1) Some secret service with the intention to make BL issue a hasty denial and perhaps this was indicating where he may be. Or,
(2) Al Qaeda, for in the past rumours of his death or illness have accompanied as a smokescreen a change of location of BL.

Wolfgang (who'd love to be proved wrong here)