I'm not convinced this was a user made level but think that it was someone (ChangKhan?) at Raven who released an anonymous level. Why?
i) it's based on the Pit level and keeps some of the features that are in the Pit but are decoration only and it all looks too identical to be merely a copy.
ii) the text file details all the saber variables to such an extent that I reckon only someone with extensive knowledge of them could have written them (and no-one on these forums seems to have that yet - no disrespect, just an observation that no-one's posted the info yet.)
iii) the scripts for respawning and setting up the final confrontation with you know who (and also getting all the music in too) was down with BehaveEd but I don't know if anyone here has actually managed to work out what the JO commands for ICARUS are yet - so could it be someone with access to the GDK at Raven?
iv) someone knows exactly how to set up the func_breakables and other entities to use them correctly. As of this time, they are undocumented and a user could only guess from working with EF and Q3 and again, no-one has indicated that they know how to do that yet.
v) someone knows exactly what enemies to mix together to give an increasing level of difficulty in the ladder. Again, not the most obvious thing unless you have inside knowledge or documentation.
Of course, I could be reading too much into this but until the person who released it steps forward I will go with my instinct which says it's a Raven person releasing it anonymously.