In concept, the idea could take a small market share from G*, but openx is not quite there yet as complete full scale and all round solution no matter how many servers are in the cluster or clever load balancing you do, the software needs a lot of improvements to compete with the likes of G*. As it is, with minor adjustments and tweaks, yes it is a solid open source solution for a small scale enterprises, up to hundreds of thousands of impressions, BUT not millions of them daily without starting to hick-up.
It has improved over the years and version 2.8.5+ upwards seem to be heading on the right track, but as an independently hosted solution, it lakes many needed plug-ins/modules, themes and technologically built-in features which are widely available in popular open source solutions and CMSs such as Drupal, Zikula, wordpress, Joomla etc.
However, let's not knock them, openx is the best open source and free ad server available today, though there are few who wrote their own that may be better or less complicated.
I wrote a Perl based one and never used it years ago, not quite the scale of openx, but at least I thought of hooks and future usability from the start for modules (plug-ins), themes, payment gateways and database backend scalability / compatibility from mysql to oracle and that was 2002. I never got it out on alpha, not even pre-alfpha, I foresaw the demanding efforts needed to maintain such a huge undertaking and shelved it. I could've launched it as open source (probably would in the future), it wasn't perfect, and I wanted a perfect core to build on and extend, perfect and solid hooks to just plug and go, a framework and codebase which was too demanding I guess and saved myself the embarrassment.
Good luck to them, but if they will base their ad solutions on the current version, they are heading for trouble unless a complete re-write has been specifically done for this purpose which is quite possible!