commercial software longterm storage

I know when a software company is working on software it is stored on version control systems on servers with backup. But once software is finished what storage medium do they use to store all their past software? Is there anything beyond burning to DVD that would be more secure and permanent?

Shitty source code in shitty languages. Nobody cares what will happen to it in 4 years.

>>1
Depends on the company, and how shitty the program was. Great companies archive their shit, with dates and notes everywhere, and just keep it on a Hard drives and make another backup on a NAND SSD. And by notes everywhere, I mean everywhere, even on the filesystem itself. Take for example FreeBSD, and learn their process of version control and archival.