They didn't.
> VeraCrypt has been licensed under the Apache License 2.0 since 28 June 2015.
> VeraCrypt inherited a substantial amount of code from its TrueCrypt predecessor and thus is also subject to the terms of version 3.0 of the "TrueCrypt License" which is unique to the TrueCrypt software.
http://lists.freedesktop.org/archives/distributions/2008-Oct...
In actual legal practice? Probably not if they want to retain anonymity.
Which may be tricky.
In the civil system, which is where copyright resides, you can simply be represented by counsel and never appear at all :)
This happens all the time.
On the forms they have, there is a space you can fill out for claimant name, and one for author name. There is also a pseudonym checkbox.
They will happily let you register it only in the name of the pseudonym.
See: http://www.copyright.gov/fls/fl101.pdf
For more interesting fun, read the last sentence of that PDF, where it goes on to explain that you get different years of protection for distributing under a pseudonym vs if your identity is revealed.