This info looks somewhat suspicious (demiurg, I am not questioning you, just LH ). LH lists this lounge as accessible for all *Gold as well, which would make it the only CO-operated *G lounge in the system that I know of I am not sure what gates LH operates from at DEN, however for what it may be worth, www.staralliance.com lists the following lounges at this station:

1) UA *G, concourse B, gates 31-33
2) UA *G, concourse B, gates ? (appears to be "symmetrical" to the previous one)
3) AC contract lounge, Concourse A

Edited to add: It looks like the CO lounge is also in Concourse A. Could it be the same one as AC? Even if that is the case, I still doubt it has full *G access; probably limited to just a few select *A carriers, LH being one of them.