Note its pretty trivial to maintain an Ant build as well as a Maven build if folks really have an aversion to Maven. There's really no reason at all to disallow a maven build from being created; they can both happily coexist - and its also a pretty trivial bit of work - not some huge bit of R&D thats gonna slow down development on other things. Also note that a non committer has already contributed the patch already for you - so no more work is required other than committing it
Its worth remembering that pretty much all popular Java software at Apache is now released into a Maven repository...
so if folks stick with Ant and refuse to allow a maven build to coexist with the Ant build, someone should volunteer to figure out how to hack the Ant build to release ZooKeeper into the Apache maven repository - otherwise its pretty hard for folks who do use maven to reuse your code (and see from the repo how many Apache projects we're talking about not being able to easily reuse ZooKeeper).
i.e. as part of the move to the ASF and being a good Apache citizen, I'd recommend hugely that as a minimum ZooKeeper releases its jars into the Apache Maven repository like most other projects do.
The easiest way to do this is just to reuse a Maven build to do releases (there doesn't yet seem to be anything in the Ant build to do actual signed releases or deploy builds anywhere) - and let folks who prefer Ant to stick to that for day to day development.
The easier it is to reuse a project, the more likely it'll get used and the more likely you'll get contributions; at least thats my experience at Apache. That doesn't mean you have to force your Ant-loving developers to switch build tools!