Integration with IMSLP
I don't think he understands how the MW extension i18n process works. The first step would be to thoroughly explain how it works.
Is there any documentation or webpage describing the i18n process?
So you wrote: "Hi Siebrand! Many thanks for your link. I've been reading the info, however I don't think all the concerns are addressed there. The main one was to "support user translations out of the box", that is, to use the current translations until everything has been migrated to TranslateWiki... I think there is a lot of "Copy and paste" work to do there... but I might be wrong... Have you ever done a migration like that before? My php skills are almost zero, but if you could take care of the technical part, I could surely take care of the line-by-line migration. What do you think? Are you up to it?" (please do not create a new thread on my talk page).
Our standard reply is: If it's a MediaWiki extension that users the standard MediaWiki internationalisation, and if it is in http://svn.wikimedia.org/svnroot/mediawiki/trunk/extensions/ we will support it. Otherwise, we will most likely not be able to support it.