Some of the oldest ones are probably in the public domain, but I guess the others are still copyrighted; nevertheless, I trust the Internet Archive will have that figured out as they have collected plenty of other copyrighted material before this.

Archives have some pretty broad exceptions to copyright infringement laws.

[0] http://www.copyright.gov/title17/92chap1.html#108

The Internet Archive hosts all of the MAME ROMs, many of which are still copyrighted:

https://archive.org/details/MAME_0_161_ROMs