Most commonly (and traditionally), RSUs are "real shares" of common stock, just wrapped in another layer of requirements (e.g., vesting schedule). This is not always true (e.g., Facebook and "phantom shares"). Regardless, RSUs have a value that is pegged to common stock.

RSUs =/= restricted stock; however, people tend to use the terms interchangeably. A RSU isn't a real share until it vests (at which point it becomes a common share), while restricted stock is a real share that has vesting requirements or some performance requirements (or both).

So the bigger point here is that RSUs are worthless... until they vest (at which point they aren't RSUs anymore). So, technically, Juno is being incredibly generous by offering any value whatsoever for RSUs ("unvested stock").

Now, even more technically, RSUs do have value and are kept on company books at the same value as the underlying stock. But they don't have value to the RSU holder.

And unless you have an acceleration clause in your equity agreement (which most people can't negotiate until they're pretty senior), those RSUs expire with a $0 value. (The value of the underlying stock drops to $0 because the corporation no longer exists.)

Restricted shares // RSUs are real shares, as long as they have vested. Restricted refers to the fact that they need to vest, as well as some other terms typically attached, like transfer restrictions.