Search multiple wikis
This could have been done by modifying the source code. "Unlimited instances" is first related to the indexer, meaning you have a server with several MediaWiki-installations and whish to index all with a single nightly cron job.
Could you possibly elaborate on that? I have a Wiki family (single server running multiple wikis, each has a separate database) and would like to be able to search across them.
This is no standard feature of ZSL and would require approximately several days of investigations and development. Unfortunately I can't provide this on a non profit base. This could also be a preformance related issue and may fail. We currently have no experience on doing so. If all this doesn't matter you could require a quote on www.wiki-service.biz. You could also check an alternative enterprise search engine like Solr.
c u stevie