I agree that Google Play Services is not competition friendly, but that is a different topic.
It's free to get one though, but it only lasts for a week or so. You can pay to become a developer and I think you get one that lasts a year instead.
Iff you have a Mac. And even then, you need to recompile it every week.
I'd prefer something else for my personal toy applications so I don't even need to bother with this, but it's not a huge deal to me.
The advantage of the Free Profile is that (afaik) it can't be revoked or censored. Disadvantage is 7 day lifespan.
Not really. You have to pay the ransom^W^W$100 for a developer account every year.
The installer is a piece of software made by Apple, to install things that meet certain criteria(ie signed packages). It's not that you can't technically "install" other things, but there doesn't exist a mechanism to do so.
At the end of the day, you can compile and run anything on your machine. This is just regulating distribution. Given the specific breaches at hand by Facebook and Google, a balance seems to have been found (acceptable to most users) between freedom and security.