My application uses Lucene 4.1 and provides two different search syntaxes, the standard query parser syntax and an approximation of dismax search that Solr has. Solr now has the eDismax search that combines the two, that would be perfect for my application so I could provide a single interface that supports both syntaxes.
But is eDismax available within latest versions of Lucene as I have no requirement/desire to rewrite my code for Solr ?
No, not really.
The current implementation of EDisMax ties into certain Solr features, so it would probably require a bit of a rewrite to yank out the related parts. You can see the implementation (for 4.7.0) on grepcode (for easier navigation) (or Apache Lucene SVN for current trunk).
SOLR-2368 is the original issue that tracked the implementation and is a good place to start digging for implementation specific details.