I was wondering does bidium focus on a specific job for freelancers? or is it a typical freelancer site wherein all jobs are available? I'm just curious. hoping it reaches alot of freelancers, you don't see a 0 zero transaction fee site everyday. 
In addition, how do they will gain their profit if the transaction fee for freelance services are zero? I don't think bidium will benefit much by this services since their website will use to provide an adequate services in freelancing. If it was zero fee transaction then it is just in favor for the clients. Well, I think this is a strategy of this project in order to gain many clients and freelancers.Your last thought hit it. As with many other existing free online freelancing services, Bidium needs to increase its network reach.
The more users Bidium have, the more chances employers have to find the right freelance worker he needs and the more employers listed in Bidium, the more the opportunity for freelancers to land a job of their expertise. And remember that as with any service, there is profitable gain in every successful transaction (directly and indirectly).
Anyway, I do not think that transactions are absolutely zero. For sure, there charge in the freelancers not in a transaction but in other ways such as monthly payment or etc.