After a couple of months of trial and error and with the kind help of the metavid / mediawiki community, I have successfuly reached a properly working installation comprising of:

Installed software

Product	Version
MediaWiki	1.16alpha (r52874)
PHP	5.3.2-1ubuntu4.18 (apache2handler)
MySQL	5.1.66-0ubuntu0.10.04.3

Installed extensions

Special pages
Semantic Forms (Version 2.2.1)		Forms for adding and editing semantic data	..., Stephan Gambke and Yaron Koren
Parser hooks
Cite (Version 2008-01-31)		Adds <ref[ name=id]> and <references/> tags, for citations	Ævar Arnfjörð Bjarmason
External Data (Version 0.6.1)		Allows for retrieving data in CSV, JSON and XML formats from both external URLs and local wiki pages	Michael Dale and Yaron Koren
ParserFunctions		Enhance parser with logical functions	Tim Starling
RSS Reader (Version 0.2.3)		adds an rss tag	Artem Kaznatcheev
Semantic MediaWiki (Version 1.4.2)		Making your wiki more accessible – for machines and humans. View online documentation.	Klaus Lassleben, Markus Krötzsch, Denny Vrandecic, S Page, and others. Maintained by AIFB Karlsruhe.
Media handlers
OggHandler	(r42524)	Handler for Ogg Theora and Vorbis files, with JavaScript player	Tim Starling
Other
MetaVidWiki (Version 1.0r47961)		Video Metadata Editor & Media Search	Michael Dale
Semantic Forms Inputs (Version 0.4.1)		Additional input types for Semantic Forms	Sanyam Goyal, Yaron Koren and Stephan Gambke

The latest extensions added were :

-ExternalData 0.6.1
Minor code changes were required since it failed to download any data from external urls.

-Semantic Mediawiki version 1.4.2 (required by Semantic Forms 2.2.1 and Semanti Forms Inputs 0.4.1)
This required quite some code patching which was performed based on the patch files as provided by George Chriss at https://labsconsole.wikimedia.org/wiki/Nova_Resource:Metavidwiki/openmeetings_v_metavidwiki
I had to apply the patches by hand since my code was a bit different and the patches failed using the patch command.

-Semantic Forms Inputs Version 0.4.1 &
-Semantic Forms 2.2.1 to provide extra input type fields, used for entering various data using a more user-friendly interface.

A strange behavior was experienced at first, since when adding a new Form (by using the special Create new class page) resulted in creating a Stream:pagename instead of a Form:pagename. Only the Form creation had this issue, Templates, properties and categories were properly created by the same special page.

I believe that the way I fixed it was adding to LocalSettings.php the following variables:

//set up namespace
$smwgNamespaceIndex=100;

//set metavid namespace to smw namespace + 10 Initially it was +6
$mvNamespaceIndex=$smwgNamespaceIndex + 10;

//add the new custom namespace index for Form and Form_talk
define("NS_FORM", 500);
define("NS_FORM_TALK", 501);
 
$wgExtraNamespaces[NS_FORM] = "Form";
$wgExtraNamespaces[NS_FORM_TALK] = "Form_talk";


Unfortunately, I'm not fully sure that the above changes/additions actually fixed the Form creation problem since I got impatient and performed a couple of changes at once. I will test to see which change actually fixed the issue.

The current open issue I'm working on is with the thumbnail creation of videos using ffmpeg. In George's patches 'thumbnailer' is used and I can't find this s/w so I will need to substitute it with ffmpeg thumbnailer .

Regards
Ioannis