The criticisms of song "ownership" expressed in this thread are all well-spoken and valid in certain contexts, but irrelevant here.

That's because we're talking about the customs of small groups of individuals who have freely chosen to associate.

Customs often seem "silly" to outsiders because there's always a certain component of arbitrariness to them. But they are quite rational, GIVEN certain goals. If you share the goals, the customs make great sense.

So, what's song ownership all about?

1) It is a way of minimizing competitiveness. If only one person sings the song, comparisons, whether voiced or thought, implicit or explicit, don't get made. That's why the rule holds even if the owner isn't there.

Now, if you think that competition is an unalloyed good, then a group that tries to minimize it might not be the one for you. But there's nothing ethically, morally, or legally wrong or irrational with a group trying to minimize competitiveness.

2) It's about place-holding. If certain items are reserved for certain members of the group, they are guaranteed to have a place in the activity. Granted, that might deny a place to a nonmember, but the presupposition here is that members have priority.

Now, if you think that membership in a group should carry NO perks, then a group that bestows perks on its members might not be the one for you.

3) Place-holding leads to a larger issue. It's about the special respect that the group shows a member of the group. Members the group get it, non-members don't. This special respect is one of the perks mentioned in 2.

4) Ownership is also about dues-paying. Newbies don't get the same treatment as old-timers. Newbies have to learn their place. But, a newbie who gets toasted for singing someone else's song AND graciously treats it as a learning experience AND comes back, passes a test.

Granted,
Small group "rules" can be quite pernicious if they are the norm for an entire society.
Formal law has constantly and consistently limited the options for small groups.
But small informal groups still have some "wiggle room" and the issue of song "ownership" seems to me clearly to fall in this category.

Admittedly, I've been on both sides of that fence.
But I currently have little patience with outsiders who crusade to get things done their way under a smokescreen of efficiency, morality, and pseudo-rationality.