As pointed out by @genava55 on the forums, the current Gaul team bonus (technologies −20% research time) is rather problematic, because the Gauls were not really technological advanced, and there is no good reason why their allies ought to be.
This patch replaces with the team bonus with a 15% cost and time discount on Blacksmith technologies, which is historically justified, since arms were one of the major export products of the Gauls.
See also D2668.