The Welcome page answers this question.
Mazix is completely Free Software and you are not forced to pay any amount of money for this game.
Foreword: Every level that isn't reachable via the GUI in Mazix is unsupported and might be completely broken. If you want to try them you are on your own. Anyway, there isn't any more levels yet, because it is still too early, but we will add them in next releases.
Mazix is licensed under a Free/Libre Software license called GNU GPL V3. Basically, this means that everybody is free to download, distribute, and modify it. Moreover, anyone can distribute modified works of Mazix, as long as those works are disributed under a GPL compatible license. In other words, Mazix respects your software freedoms.
All the things you need to know to compile the game can be found in the Development section.
From the beginning, there is only one active developer on the game and he is also involved with a heap load of other projects, so it takes time to find time to develop on the game. Help is of course always welcome.
Have a look on the recommended system requirements on the Welcome page. If your system is all right, try to decrease your screen resolution.