You know, I remember when that quote from Barry Finn was first made and, with all possible respect to the guy, I didn't agree then either. There are all kinds of singing venues, and I think they are all represented here in one way or another. A gig, especially a paid gig, to me means that the performer knows his material and memory aids should be limited to a cue sheet with the song order - doesn't always work for everyone, of course. A group sing is a different critter entirely and, as has been said several times, local custom governs.

The term "singaround" used by the OP means different things in different places, and stating that such-and-such is permissible at a song circle or a group singalong but not at a singaround is essentially meaningless. There is a great mix of styles where I "sing"; some participants are confident enough to sing without aids, some like immensely complicated 87-verse ballads for which lyric sheets are essential and some like to sing as part of a group, in which everyone is singing the same thing in the same way. We take turns. Some of the purists out there will certainly say that one or more of those is wrong...and I suppose it is - for them. Some of us do not have the advantage of living where there is another group singing in a different way on another night at a different pub ten miles in the other direction or living in a major metroplex where there is something to fit every taste.

BTW, "Rise Up Singing" and "The Folksingers Wordbook" are very different publications, both are in print, and neither is a precursor of the other.