You kind of make it sound as if his brain tumor is more of an annoyance to you and your company than to him.
What about the truly hard questions this might bring up? How do you plan for the possible long-term absence of a founder without ruining their hope of beating their disease? What happens to the equity of a founder who passes? Is this something you need to discuss with them, along the lines of a will, to get straightened out? How do you deal with employees who might also be experiencing emotional grief over the situation? Are there situations where you need to slow the growth of the company so people can deal with their personal reactions to a situation like this? How do you cope with the dual emotional roller-coasters of running a start-up and having a friend on death's door?
Any of these would be interesting questions to hear responses to. Instead, this article chooses to take the shallowest route possible and actually treat the horror of cancer more like your co-founder got the flu and was out for a week or two...
Chances are, if he hadn't included the bit about how he's handling his startup, you wouldn't be reading it here.