That is not a tank. That's an armored car.
A tank requires three things: heavy armor, a turret-mounted gun capable of anti-tank combat, and the use of tracks instead of wheels.
This arguably fails all three. It's a wheeled vehicle, and that 7.62mm gun may as well be paintballs to other tanks - it's a common caliber for the coax gun on modern tanks, for use when you don't want to waste your expensive ammo against mere infantry. The armor is definitely insufficient to handle modern tanks, but it would have been enough for 20's and '30s tanks (or perhaps WW2-era Italian or Japanese tanks), so you could probably squeeze it in.
That said, as long as the rebels use it intelligently, an armored car is a very useful tool. Keep it in the cities, where tanks have difficulty maneuvering, but use its mobility to outflank infantry. It will be interesting to see how long it lasts - it doesn't look like it could handle modern anti-tank missiles, but it *might* stand up to an RPG-7 or so.
It's certainly true that this does not come close to the commonly accepted definition of "tank" since the 1930s. However, it's interesting to note that the term evolved quite a bit from its first use. The original tanks in WWI did have tracks, but they did not have turrets, anti-tank guns or thick armor. There were designed to protect the crew from enemy machine gun and artillery fire, which is probably all this vehicle is intended for. The RPG-7 can penetrate at least 260mm of steel, more than ten times the thickness on this vehicle.
