Manual:$wgEnableOpm

HTTP proxy (CDN) settings: $wgEnableOpm
Use opm.blitzed.org to check for open proxies (never implemented).
Introduced in version:1.4.5
Removed in version:1.7.0
Allowed values:(boolean)
Default value:false

Details

Use opm.blitzed.org to check for open proxies. According to the documentation this variable was never actually used.