There are responses from dkubb and wycats, and the conversation shows it's not that simple and that there are other perspectives, as is often the case.
True, he did generate a SWIG wrapper to create the first prototype of DataObjects after a conversation we had where I suggested Ruby would be a better place with an ADO.NET-like database interface... but none of that was really usable since you had to have the exact same MySQL version down to revision, on the same system. The only other major contributor to DataObjects outside of the Wieck team I recall (and apologies if I missed anyone) was Dirjan Bussink fixing my broken Connection Pool. Later contributors (and Dirjan) ended up rewriting a lot of it for Asynchronous Execution, more driver support, etc. But that's the reason the thing looks so much like ADO.NET.
Oh, and Command#set_types was me too. Which is the reason DO is the fastest (last I bothered to look) database API for Ruby.
The marketing contribution was HUGE. It always surprised me how many new people showed up after one of Yehuda's presentations. DM wouldn't be what it is today without Yehuda. But your own opinion on DM's code is about as valid as Yehuda's. Just look at the commit-history.