We have stopped updating the MIB guide from 6.4.x onwards. The MIBs descriptions are now part of the aruba-mibs_6.x.x.x_<build #>_tar.gz file. Unzipping this file will give you all the required information. You can download this file from the Download Software tab of the support site.
A snippet of the aruba-trap.my file follows:
wlsxTrapRogueIfoURL OBJECT-TYPE
SYNTAX DisplayString(SIZE(0..64))
MAX-ACCESS accessible-for-notify
STATUS current
DESCRIPTION
"
This object is used to point to the WEBUI Rogue AP information URL.
"