Ning 2 > Drupal 8

I finally published (as GPL) my migration from Ning 2 to Drupal 8.1
(I migrated from Ning 2 to Drupal 8.1.1 in may 2016).
I now also have a migration for 8.2.4 (only draft published: if in urgent need, use that, or migrate to 8.1.10 and update to 8.2.4 or contact me). Also did draft for OpenSocial: will not elaborate on that more (that's site building). Instead will provide a more simple sample distribution with the "groups" module only and a generic post content type.

Use Cases:
It's a starter kit that might save some migration cost.
It might also be interesting for the sample data and
even for non Drupal destinations (although the generated
intermediate csv is strongly tailored against Drupal).

Destination System, Limitations:
The first draft was Ning 2 -> 8.1.10 .
Destination is pure Drupal 8 core, no whistles and bells at all.
Groups are only mapped to a site type node+forum, no ACL;
membership is conserved as multiple entity relationship.
Audio, Video are not handled. Blogs become a forum.
Users are migrated with profile questions (weird ning json ..).
Discussions, events, notes, pages become nodes.
Forum categories become taxonomy, just like the group forums.
Comments are migrated for all nodes. User profile comments
are not yet handled (missing: handle left/suspended:
that still confuses re-numbering of the comments:
renumbering is required, because Drupal cannot set cid).

The tool chain is:
a:ning2export --b:preprocessor--> c:CSV --d:migrate_ning2--> e:D8 core

The package consists of
a: sample data for the json
b: the preprocessor (C++ source and exe)
c: sample csv generated from preprocessor
d: the migrate_ning2 module and helper contrib modules (patched)
e: a Drupal 8 core configuration and files as well as
e1: pre migration dump: activate migrate modules and import sample CSV
e2: post migration dump with the imported sample CSV included

Note that the migration is very unconventional
in that it does not use Ids generated by dependency
migrations and managed by the migrate module,
but instead uses a preprocessor (C++) which
transforms the Ning json (sometimes corrupt json)
to CSV, which is imported using migrate_source_csv:
the preprocessor does the bulk of the work:
it creates or renumbers ids where required/configures
and thus also can transform the html such that links
are relocated to drupal too: this is used for inline images
but also intra-content links. For comments, it uses a trick:
manipulate AUTO_INCREMENT to control id generation
(unfortunately the API does not support setting the comment id).
It also handles character encoding (ning encoding to utf8),
filtering of left/suspended users (content partially in ning dump).
The preprocessor has evolved from a json reader (check and
correct corrupt ning json export) and is a little complex,
but it has many configuration options and produces an
extensive error log. If more than configuration is required,
feel free to ask me via my Drupal profile.

I want to clean up more, but if somebody is in a hurry ..

Plan/Status as of 20 April 2017:

• x adapt for 8.2: done, but only draft published, see download link.
• I also did a draft version for Drupal OpenSocial distribution . I will not elaborate on that any more than the draft (too much sitebuilding, quitting the way of a generally usable migration starter kit): critical points are: Ning Networks often have forum categories, forum like groups, closed groups: how can the forum category structure be integrated in the OpenSocial Taxonomy, which is too simplistic/formalistic?
• x cleanup: include newest migrate modules, test with current drush
• @ version for Organic Groups, using D7 (not yet published). Will publish only when I updated doc, extended test data did the same for D8 with module "groups"
• - port preprocessor to Linux (currently Visual Studio, Windows)
• - cleanup: handle language better (current is german/DE single language)
• - bug: handle profile comments (currently not imported)
• - bug: handle timezone problem for event dates
• - feature: maybe switch to date with end date (new D8 field type in 8.2)
• - maybe I can get sample data for Audio/Video soon.

D7 solution
I also published the D7 version as GPL (but I never used it in production):
https://www.drupal.org/node/2321831#comment-9809851

D8 download link
With readme documentation, screenshots, download zip file:
http://www.r5c.de