I don't want to read the source code, I want to use the product. If there is a bug, I want you to fix it. If you don't fix it, why am I paying you / using it? Assuming I am a programmer (many users aren't) and make my own patch, and you don't merge it, I'm still screwed. Source only helps me if I'm the one running the code. So the fact that your SaaS is source available has no bearing on my use of it.