For one thing, open source isn't really free. It requires you to make your own code open, which isn't very helpfull for commercial software.
Now, this statement is just plain incorrect. Some licenses DO require you to open part of your source and distribute with the same license (ie GPL), but others (BSD) are fine with commercial distributions.
Also, lets say someone does an open-source driver you want to use with a new (closed source) package you're developing. Simply write yourself an open-source API to use the open-source driver, and keep then write your CLOSED SOURCE APP to use the open API. That way, when a new Wacom tablet comes out that breaks the previous driver, someone can write the new driver to the API spec, which should plug into your app without needing any source to your app. (they've got everything they need in the API) Doesn't this make more sense?
