Open RPG Maker is a free and open source clone of features from the RPG Maker series (i.e. rpgmaker200, rpgmaker2003, rpgmakerxp), as well as many other features. All of the data files are in XML format and are easily editable with any text editor.
I did not read that this would not actually make a game so I was very disappointed when it could not. I do hope you guys finish it soon. :-) Some thoughts: A)The icons are really small and jambed together making it hard to both see as well as decide if a certain tile is what you want to use. Maybe make a detachable area to view the tiles with? Or just put a little white space around the tiles? B)Only accepting PNG images. There is a library on Source Forge (somewhere) that allows you to load in something like 200 different file formats. Internally you could convert them to being PNGs but there are tons of GIF images out there that could be imported and they also use transparency. This would also allow you to load animations. So characters walking, trees swaying, etc.... That is all that I see right now. I would have given you 5 stars - but it doesn't compile yet. Everything else - if I had to - I could live with. Great work! Keep it up!
I've been trying it out, just started, so take what I say with a grain of salt. However, apart from being able to run the game (which you guys are already working on), it would be nice if when the game can actually be made (or compiled) we can see the source-code of the game, and even edit it (sort of like Kompozer, but instead of webpages, it's an RPG). Other than that, I think this is well on its way to being a great game maker for both Linux and Windows.