If he doesn't explicitly state a licence, the default copyright is owned by the author. Open source licences exist for this reason, to change the "default behavior" of something that is publicly released.

For this reason Kwerty owns the rights of distributing and using his code even without a licence.

I didn't even consider it, as I created the app for fun and just wanted to put it out there.

I looked at some of the various types of licenses but I have no idea which one I should be using.

My main concern is to prevent people from trying to profit from the software. Any suggestions?

BSD/MIT (and maybe Apache?): People can take your stuff and resell it.

GPL/LGPL: People can't take your stuff and use it in any way whatsoever without making what they make with it open source as well.

That may be a broad generalization, but it's mostly true.

Even without a license, this is still a copyright violation for distributing something he doesn't have rights to.