Correct: the right to distribute a game with that branding and those mechanics is valuable if you have the means (such as any copy of the source) to do so.
The source by itself is hardly (monetarily) valuable, pretty much to anybody. Blizzard clearly still has other copies, and anybody else wouldn't be able to do much of anything commercially with the code.
It's quite possible somebody has even already reverse engineered much of it, rendering it even less valuable by itself, even to copy-cats.
The code doesn't have commercial value because it contains no secrets that would allow you to implement a competitor to Starcraft HD/Remastered.
The code doesn't give you the legal permission to distribute and brand a game Starcraft.
The reality is the code has no commercial value, the brand on the other hand may as well be a license to print money.
No. They're using the same gameplay code as the original Starcraft:
Q: How did you go about replicating all the unexpected “bugs” that made BW micro
so special? Did you simply reuse code from the original game, or did you find a
solution to replicate the nuances of BW’s gameplay?
A: StarCraft: Remastered is able to achieve this effect as it uses all the same
gameplay code as Brood War. This means that Dragoons and Goliaths are still a
bit derpy in how they react to movement commands. The Reaver’s shot doesn’t
always find a target. Mutas stack.
The fact is that the gameplay is identical enough that old replays from 1.16
will play and work just fine under StarCraft: Remastered.
The source by itself is hardly (monetarily) valuable, pretty much to anybody. Blizzard clearly still has other copies, and anybody else wouldn't be able to do much of anything commercially with the code.
It's quite possible somebody has even already reverse engineered much of it, rendering it even less valuable by itself, even to copy-cats.