Teiid is a [big] subset of Redhat Data Virtualization (RHDV) system. However, RHDV has other modules like Modeshape. It is also a fully tested version by Redhat QA and supported on various platforms. If you are looking for support/service/training with SLAs then RHDV is for you.
Teiid is upstream open source community project that feeds into RHDV. Teiid does NOT come with any production support, you have to depend upon community members for any questions you have. Also Teiid release cycle is rapid (3 months) to provide new features in timely manner. There are few more differences like that.