Hi,

I was wondering if there exists an open source equivalent to Gomobo.com product?

Depends on whether you want fries or not.

I have not been able to find a product that provides this service. 

However the overall concept isn't too complex. A message needs to be
received, compared to a user database (by sender number) to expand the
shorthand order favourite into a full order, and then forward it to
the vendor by email or fax.

I may be able to provide some links to services to handle SMS
messaging, and make suggestions about how to interface with that
information