3.3.0 is mostly a maintenance and QA release. The major news here is that we've done an AI-based (Claude Fable) review of all the code, this has resulted in quite a lot of hammering on the code to get all the issues found smoothened out.
3.3.0a1 is a variant without any http-library in the dependencies - allowing projects that bring their own http-library to pin a caldav-version that does not bring in niquests.