At first I didn't see how allowing others to put up financial barriers would encourage freedom, but I guess share-alike works for me to.

The asset license has been changed to CC-BY-SA.

I disagree on the keyboard input. Note how you can combine two keys on the numpad to aim in sixteen different directions.

Mouse aim has been considered and might be implemented along with input options. I would really advise you to find a second controller, though.

Walking out the door (top) exits the game.

I believe the correct spelling is houndsome

Rars are not well supported in Linux due to their proprietary nature. Tar.gz would probably be most preferred, but zip is fine too.

The AsteroidX file was not recognised as an executable file but as a shared library and I had to chmod u+x it in a terminal to be able to run it. It only gave the following error message:

error while loading shared libraries: libstdc++.so.6: cannot open shared object file: No such file or directory

I'm running Xubuntu Linux 64-bit

Back when I still used Unity I found UTiled to be the most convenient free option. It has its limitations but suited my needs at the time.

I switched to Urho3D a year ago which has built-in TMX support through C++ classes. It's library is very similar to Unity's yet allowed me to return to Linux.