Yeah, I'd try asking on a commons-validator mailing list/forum, or simply looking in the source, since it's available.
I'd also point out that commons' email validation, at least as of 1.2.0 and 1.3.1, doesn't necessarily check for valid top-level domains. From the API:
For example, an address like nobody@noplace.somedog will pass validator, even though there is no TLD "somedog"