It's MIT licensed. It's not clear to me that it's developed by jetbrains at all, but if it is, there will probably always be an open source version, if only because it gets forked.
I believe there is some ‘official’ support for that plugin, I vaguely remember reading that JetBrains was devoting a small amount of resources to aid in its development. Though I can’t imagine it would effect the license
The author of the plugin works at JetBrains and works on it on his day job.