The eclipse Lyo project has the UML models for OSLC Core in org.eclipse.lyo.docs/org.eclipse.lyo.model/OSLC-V2/OSLC-V2.emx. RSA is required to edit these .emx files. It is not an open-source, or free tool, so it isn't really suitable for open standards work. There may be restricted licenses available for standards work, but this isn't required for me since I work for IBM. For now I'm going to stick with RSA in order to reuse the existing model content.