Well spotted. It is indeed a bug. The shipbroker code was changed a couple of versions ago. The new code is working in SOTP but VOTG hasn't had the new code added yet so you can't buy ships.
As ferdinand says, VOTG is still an alpha. Game balance is secondary to getting the mechanics of the extension working at this time but George appreciates all feedback.
You could try running PM's mod GodMode http://xelerus.de/index.php?s=mod&id=799. This works in SOTP and VOTG. You can change things like currency levels to make it easier to 'play' the VOTG alpha until it is a bit more balanced.
PS: You can also blast and loot friendly hexacoral colonies without being attacked or penalized ATM.