That's correct Marcus and we should be very clear here. Global Search will be implemented in a way to allow for plugging other search engines than solr but at this moment only solr support will be implemented.
To make long story short (I've spent quite a bit of time on this): there is no search engine written in PHP, so it's either Java or nothing. I doubt anyone will ever implement support for anything else than solr.
We will depend on solr features as well. For example text extraction from documents is provided by solr, so we will not be implementing our own text extraction.
Because of the above, Global Search will not work with Moodle out of the box. To get in setup you will need to get Java hosting, setup solr, add PHP extension that talks to solr, etc. We will of course produce installation instructions.
Hope that helps,
Tomek