They are allowed to make it closed-source, and there's no shame in making well-maintained commercial software. That's how business works.

What about when business fails though? Open-source projects never die; see the forks and reused knowledge in projects such as ffmpeg, libav, iPodLinux, Rockbox. For archiving purposes, open-source is tremendous.

I wish another kind of license were available, where software remains commercial until the company closes down, but then becomes OSS rather than abandonware.