Semi-currencies are theoretical tokens of value which can be traded in exchange for a limited set of goods, rather than acting as a full legal tender. As such, they could be exchanged for far more value than legal tender, could be issued and controlled by entities other than the government, and could facilitate barter between citizens.
They could imaginably be issued by private citizens as a promise of labor, or be issued by employers to denote the kind of service rendered, or that service had been rendered to a particular employer or department. This could make for more or fewer headaches in accounting, employment, and economic regulation.
Your guess is as good as mine. Care to make a wager or comment?