Yes, Zend_Search_Lucene was dropped from Zend Framework 2 and never officially maintained for modern PHP. There's a community fork.

Any idea if it's any good? I used the old Lucene implementation ages ago and thought it was OK, though wasn't using it in a big way.

The zf1s/zend-search-lucene fork still works and gets occasional updates, but it's essentially legacy maintenance on a PHP 5.3-era codebase. It crashed on PHP 7 for a while, and the original ZF team themselves recommended moving on.