We currently don't have an option for the user. The reason it's an error is because the each Designer release is targeted at specific Teiid runtime. This includes a specific VDB definition which the runtime can change in follow-on releases. There is a VDB "schema" which defines the structure of a VDB content with key/value properties generic. There is no other contract between Designer to insure that newer/untested versions Teiid will be compatible, especially if you are designing against newer Teiid runtime features.
In hindsight, it may make more sense to make this validation check configurable (i.e. ERROR or WARNING) to allow users to override it and take their chances. The ERROR states that the "VDB... may contain...", so relaxing this makes sense.
Can you log a JIRA and ask for an enhancement? Thx (see Teiid Designer - JBoss Issue Tracker)
BTW, our 9.1 release is targeted for end of Jan 2015 and this will be tested against Teiid 8.9.
Barry - Teiid Designer Project