From what I've been reading, the UIC has more or less dissolved and doesn't really exist in any active form. It was a union of courts, each of which arose independently in a specific area to address the problems of trying to create some sort of order out of chaos, and to establish a civil infrastructure. After the different courts formed the union, that union formed an armed wing. Once the UIC was chased out of the areas where they held power, they ceased to exist in any meaningful form, but Al-Shabaab remained active as a force to fight the Ethiopian occupation. However, some people who held high ranking positions within the union still consider themselves to be members of the UIC. These people have been having stark disagreements with Al-Shabaab, and do not recognize them as a part of the UIC.

I guess the best comparison I could think of would be if the US government dissolved, but the army remained and took off on its own to do whatever it decided to do without the government to act as a moderating influence.