GID collab-maint or scm_collab-maint on alioth git

[Osamu Aoki <osamu@debian.org>]

Hi,

I noticed that the alioth collab-maint repositories have GID
 collab-maint     (older projects)
 scm_collab-maint (recent projects)
depending on the project when a person complained to me that he can not
accesss one with scm_collab-maint.

drwxrwsr-x+  7 osamu  scm_collab-maint  4096 Jun  9 11:46 debmake-doc.git
drwxrwsr-x+  7 osamu  collab-maint      4096 Sep 16  2013 debmake.git

Are there any document for these group usages?
What are the differences?
Any differnces for people with -guest account?

Osamu