Yes, the manual is not very well maintained right now- I think most of its content is still relevant to the language now, but small bits like how to install are a little different. Other, more up-to-date resources for learning include the language reference , which is not just a dry reference as the name would suggest, but a mix of a walkthrough and reference, and our free online video-based course , which is based on what we teach at California Institute of the Arts. The examples are a great resource (included when you install ChucK; go to File->Open Example in miniAudicle). Graham Coleman's "Notes on ChucK for Music" is also a good tutorial  and Perry's ChucKU has a lot of learning resources centralized in one place . If you want to go a little deeper, the ChucK book  costs money but has a few free sample chapters.
The individual who generously created and maintained the ChucK manual stepped down some time ago. Producing and maintaining high-quality documentation is a big job, and with all of the other resources available, the ChucK manual has not been the top priority. That being said we would welcome pull requests to ensure the manual is up-to-date, relevant, and useful (and actually there have been a few such PRs recently).
In the last year we've been developing a number of major updates to the language and ecosystem. I have been working on miniAudicle for iPad, a tablet-oriented coding environment for ChucK, which is going into beta testing very soon, and a number of individuals have recently contributed to our growing collection of chugins --its worth checking out the new ones for ChucK coders who are looking for new stuff to play with. Small but impactful bits like more informative exceptions have been developed (and are coming to a release soon).
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