Eclipse projects, such as OCL, use Maven in the form of Tycho that adds support for Eclipse working practices such as the P2 repositories.
There is no official support for provision of releases via Maven centeal and few projects provide it. When you find an Eclipse projhect on Maven Central be aware that it was probably provided by a well-meaning but misguided Maven user without knowledge or approval of the Eclipse oroject. It almost certain that that user will neglect to provide updates and so it is just about guaranteed that what you find is very stale.
Eclipse provides an http://repo.eclipse.org for use by Maven users and some projects publish there. However there is no standard support for http://repo.eclipse.org and it appears that this approach is going obsolete. Attempts to offer OCL via http://repo.eclipse.org have foundered.