Yes, but it still is nominally communist, which means the not-so-communist USA and neighbors won't be so eager to support it.
Of course not. But in a world where, after the fall of the Soviet Union, there would be no immediately clear single hyperpower, but a bunch of competing powers, Korea might find some mutually tolerable limited partnerships. And I doubt that anyone is going to worry about them to the point of bothering with invasion and regime change, considering the likely level of general mess elsewhere. Communist Korea, in a world where Communism has failed most of everywhere else, may be no one's friend, but it would also be a very low level threat for everyone. Compare that with the destablising hassle of what to do with it AFTER a regime change (considering that, of course, Koreans would have ideas about it that external powers may not necessarily share).
It also is true that, in actual history, this sort of reasoning was often overruled by every sort of other considerations such as prestige, ideology, sheer idiocy, and so on (as in, a power or combination thereof may decide to interfere in Korea even if this is a move that obviously runs against a rational reckoning of their best interests - or, conversely, that Koreans leaders may take some obviously stupid decision that warrants foreign intervention).
In the current setup - roughly like IOTL for over a century - keeping your rivals out of Korea probably tends to be more important than actually controlling Korea for everyone interested except Japan (not an independent factor here at this point I guess). Rationally, this means that a Communist "we hate you all" Korea is moderately fine and preferable to alternatives for most actors involved
unless a) they have some other specific reason to do otherwise b) Communist Korean does something unacceptable for one or more said actors (like, say, a military nuclear program?).
All this, of course, assuming that Communist Korea survives.