I would love to create an RPG with EasyRPG. Is it already ready for use? Or do I have to buy the original RPGMaker? (I couldn’t find the development state on the homepage, nor in the wiki nor in the repo. Did I overlook it?)
If you wanted to make a game, the EasyRPG Editor is currently not ready to release games, since the development for EasyRPG was mainly focusing on the Player. Once the version 0.8.0 of the Player will be released (hopefully in around a week), the development of the Editor will start, so maybe a first release of the Editor could be done this year or the next.
Until the Editor is ready and released, you can still buy RPG Maker 2000 or RPG Maker 2003 on Steam, or you can try to use R48, another Editor compatible to make RPG Maker 2000/2003 games, though its interface can be a bit tedious to understand.
As for playing games, outside of video playback and games using patches, the Player should be almost 100% compatible with the game that you are playing.