abNinjam uses part of the original Ninjam code, which is licensed under GPLv2. Binary releases therefore have to be under the same license as well (IANAL).
It's not generally problematic to have parts of the code under MIT and other parts under GPLv2, but to avoid confusion about binary releases it would probably be a good idea to change the whole project's license from MIT to GPLv2.
abNinjam uses part of the original Ninjam code, which is licensed under GPLv2. Binary releases therefore have to be under the same license as well (IANAL).
It's not generally problematic to have parts of the code under MIT and other parts under GPLv2, but to avoid confusion about binary releases it would probably be a good idea to change the whole project's license from MIT to GPLv2.