RubyMotion now has a free starter edition for iOS and Android apps. Is there an equivalent free edition for devs building Mac OS X apps?
TLDR: Not yet, but HipByte (the vendor) does not object to the idea in principle.
Long answer, from an email exchange with Mark Villacampa of HipByte:
"On iOS and Android, the starter version adds a splash screen to the app that you can remove by purchasing a full license. On OSX, there is no equivalent of a launch image, so it is more difficult to control. In the future, we will look for ways to work around this limitation, and find an alternative way for OSX."