Yui added file sdl2/ext/c86ctl/cbus_boardtype.h which
says "This software is licensed under the BSD license."

File sdl2/MacOSX/xmilsdl2/xmilsdl2-Info.plist says
"Copyright © 2015年 Yui."

Given that the author published the source himself on freely available
site "Software" in this context can be understood to apply to the whole
package.

So unless author says other this can be assumed to be BSD-licensed.