Codesearch has been working fine in the past couple of years. There is a new frontend being built and I hope we can deploy it soon to provide a better user experience and I personally don't see a value in re-implementing codesearch. Especially using non-open source software.

While I agree with several points that have been raised, in particular about licensing and building on top of existing tools, I'd like to point out that the idea is not to re-implement codesearch, but to overcome some of its limitations. What we use codesearch for most is finding usages of methods (and sometimes classes). This works fine if the method name is fairly unique. But if the method name is generic, or you are moving a method from one class to another an you want to find callers of the old method, but not the new method, then regular experssions just don't cut it.

Basically, I'd want codesearch to allow me to do the kind of "find callers" search that IDEs like phpstorm support. Sure, I could do it in the ID, but I can't link to that from a ticket, and I'd have to make sure I have exactky the right set of extensions installed (and updated).

A tool very much like codesearch, but based not on regular expressions but rather on symbols and their relationships, would be very valuable to me. The question how exactly it should be build is of course open.

-- 
Daniel Kinzler
Principal Software Engineer, Core Platform
Wikimedia Foundation