Legal slide? Interference?

[Dakota]

This is a softball rules thread, even though the visual aid is from MLB.

Go to MLB.com and view the video of the Upton slide into 2B in the 7th inning of game 1 of the NLCS. 2 runners on base (1B and 2B at the time of the pitch).

If this was a softball game...

Was the slide legal?

Would you have called interference on the retired runner? Why or why not?

If yes, who would have been out?

NOTE: I don't care what the MLB rule is, whether the MLB umpires called it correctly, whether this stuff used to be allowed in MLB, etc., etc. It is just that this play provides a nice visual aid for discussing legal slides, IMO.