If you have a good idea, everyone else gets that good idea and it gets merged into all products - even the bad ones. But on the better Linux distributions, especially Debian, package management takes care of this. The installation of the package you want implies the installation of the latest version of all the dependencies, and this happens automatically. You will not normally get into a situation where something has to be downgraded to support a package, because most libraries are backwards compatible. This means that the real differentiation for OpenSource isn't marketshare or even marketability, but simply whether or not it can garner a following.
Market share is the goal.
The only difference is that the reward for more marketshare is different. There are also many kinds of software which have lifespans just too short to make it sensible to bind the customer in a service agreement. Games are a good example. Most games are onetime sells. In fact if memory serves, it's one of Eric Raymond's examples of software which should not be open source, at least not at first.