What is the most important feature of PostgreSQL 11?
Actually, this is hard to tell. It really depends on how you are using the database and which features are the most important to your application. Everybody has a personal favorite, however. In my case, it is parallel index creation, which will be really important to customers running giant databases. Still, it is up to you to decide what you like most and what you don't like.
Does PostgreSQL 11 work on my platform?
PostgreSQL 11 works on all common platforms, including but not limited to Linux, Windows, Solaris, AIX, and macOS. The community tries to cover as many platforms as possible so that it doesn't exclude people from using PostgreSQL. For most common systems, PostgreSQL will even be prepackaged.
Did the license model change?
No, nothing has changed and most likely nothing ever will.
When can we expect PostgreSQL 12?
Usually, a major release can be expected once a year, so the next major release, that is, PostgreSQL 12, will be in the fall of 2019.