ipv6 multicast listener on linux box acting as multicast router

Hi guys,
I would like to have your opinion on a comment in the ip6mr.c file
(kernel 2.6.29.4). The comment follows:

/*
* RFC1584 teaches, that DVMRP/PIM router must deliver packets locally
* not only before forwarding, but after forwarding on all output
* interfaces. It is clear, if mrouter runs a multicasting
* program, it should receive packets not depending to what interface
* program is joined.
* If we will not make it, the program will have to join on all
* interfaces. On the other hand, multihoming host (or router, but
* not mrouter) cannot join to more than one interface - it will
* result in receiving multiple packets.
*/

Does the part "if we will not make it..." mean that such behaviour is
not yet implemented in the kernel? Looking at the code, it seems to me
that it is not yet implemented, but I would like someone to confirm
it.

As an implication, if I have a IPv6 multicast listener on a Linux box
acting as multicast router, do I need to have my application listening
on all the interfaces if I want to receive the multicast messages no
matter what is the interface from which they are received?

Thanks in advance for your help!
Massimiliano