I have very little experience with anything but Crestron so my opinion my be more biased but I will try not to be.

With Crestron offering pretty much all the hardware (audio matrix and sources, video matrix, lighting, thermostats, and door locks) and a vast majority of the modules for security and pool integration. I can't see why there would be a lot of custom written modules for these systems so code wise there shouldn't be any reason why a dealer couldn't hand over the simpl program/s. This will allow the homeowner the ability to swap a Blu-ray player or change cable boxes without having to change an interface.

The customization comes in the GUI. Majority of the integrators spend a lot of time and money on creating a custom designed GUI that they use for all their customers. Supplying this custom GUI to the homeowner is where I see a lot of the issue with handing over the files. I don't believe the integrator should be required to hand over the interface if it is of a customized nature where they have purchased the screens and icons from a GUI design company. If a system is designed using Crestron graphics there should not be any reason why the integrator can withhold the graphic files.

With the release of Pyng and soon to be (maybe) Home Elements from Crestron I think that this customization will become less and less as the programming will become less customized and more configurable. At this time Pyng is pretty much a complete configurable system Pyng cannot do video distribution and pool control but it wouldn't cost near as much to add this to a small processor and integrate Pyng into it as it would to program the whole system on a larger processor with custom screens for each aspect of the project.