EMF Parsley is part of the Eclipse simultaneous release, so you will find it using the standard Eclipse release update site, e.g., https://download.eclipse.org/releases/2022-12/ .
Each EMF Parsley DSL version (included in the EMF Parsley SDK) requires a specific version of Xtext. Unless you install EMF Parsley from
the Eclipse releases update site that includes that specific version of EMF Parsley (and the corresponding
required version of Xtext) you should add the Xtext releases composite update site as well,
so that the required Xtext version will be automatically installed (but please remember that it is a
huge composite site:
https://download.eclipse.org/modeling/tmf/xtext/updates/composite/releases. Alternatively, you can use an Xtext specific version's update site.
All downloads are provided under the terms and conditions of the Eclipse Foundation Software User Agreement unless otherwise specified.