Everywhere else there is a distinction between virtual currency and real currency. This line just says "currency". It is quite vaque in that it could say "if the person accepts (Bitcoin) from one person and transmits it(Bitcoin) to another person as part of the acceptance and transfer of...value (that substitutes for currency)." Would that mean that every node on the network transferring bitcoins from one person to another is an "exchanger and a money transmitter"?
I think if it just says "currency", they are referring to the FinCEN definition of currency, which excludes "virtual currency".
Yeah, because "currency" here means US and foreign currency. This is a limitation of 31 USC § 5312 (a)(3). They can not just throw "virtual currency" in there. They really deserve to get slapped for trying.
Ok, that makes things more clear.
But what is meant by "value that substitutes for currency"?
Presumably the other "monetary instruments" that they are allowed to regulate under section 5311 et seq: travelers checks, bearer negotiable instruments, bearer investment securities, bearer securities, stock on which title is passed on delivery, and similar material.
But who knows really... If they actually try to enforce these regulations, these definitions will probably be argued in court sooner or later.