If you use BizForm as an inline control, you can adjust its code-behind: ~\CMSModules\Bizforms\InlineControls\BizFormControl.ascx.cs by amending the SetupControl() method. You will set the BizForm property UseColonBehindLabel to false like this (be aware of this change in case of future upgrade):

this.Bizform1.UseColonBehindLabel = false;

On the other hand, in case you use it as a webpart, there is an easy solution for that. Please locate to webpart properties (on the Design tab) where you can see the 'Use colon (:) in labels' property. You need to set it to false.

In ASPX templates you can add property to you your BizForm web part <uc1:BizForm ... UseColonBehindLabel="false" />