I think I would read it similarly to Mr. Morin, or at least it raises that question in the sense that where, elsewhere in the third party regime, we've said a registered third party has to report contributions, they are contributions made for certain purposes—for election advertising or partisan activities. In contrast, this provision just says “a list of all contributions”.
A possibility, using a slightly different example of a non-profit group that sought to conduct third party advertising would be if it did register and it had some donors who were foreign donors. It would have to report all of those foreign donors regardless of whether it used those foreign contributions for partisan activities, etc., or for their other regular purposes.
In terms of the size of the burden, I'm not sure, but it would obviously be more reporting than is elsewhere in the contributions regime for third parties.