Welcome to ChucK! It has been around for over a decade and is being used all over the world by researchers, academics, hobbyists, musicians, and so forth. It's very much still a popular audio programming language. There is an online course (which is currently out of session, but will be back in session over the coming months). It will be available at the following link:
https://www.kadenze.com/courses/introduction-to-programming-for-musicians-and-digital-artists/info. An in-depth book has recently been written by the designers of ChucK; there is an e-book. It is available here:
https://www.manning.com/books/programming-for-musicians-and-digital-artists. This mailing list is also quite a useful tool for anyone needing assistance or needing to report bugs. There is documentation available online, and there are some great example files. The example files (alongside the book) would be a great first step in learning the language.
When asking for assistance, be sure to include as much information as you can (such as your operating system and any necessary code). Happy Chucking!