I think work arounds being easier doesn't really need any empirical data to back it up. By having the source code, a lot more people will be able to make sense

I think work arounds being easier doesn't really need any empirical data to back it up. By having the source code, a lot more people will be able to make sense of it and figure out how to change (or even fork) the original software. I'd say that's pretty much a corollary. On the other hand, I think free software probably tend to break backward compatibility less mainly because it moves at a slower pace (be it because it's designed by committee or just lack resources). With software as a service in special, breaking changes is sort of the industry norm. So, there's also that cultural component to it. But it's difficult to measure the rate at which free software introduces breaking changes vs proprietary software.