I think MediaHound read .ag instead of .aq (Antarctica)...
For .gl (Greenland) see
http://www.nic.gl/uk/index.htm
At first glance it looks like there are no specific criteria fore registering these names.
Please note that I do not have experience registering in either of these ccTLDs, but I did previous research just like you. I often register European ccTLDs so I try to know about the requirements for each country/ccTLD.
Concerning .aq this is a closed ccTLD.
It is sponsored by
2Day Internet Limited from New Zealand
http://www.iana.org/root-whois/aq.htm
I actually contacted them (I think it was in 2002) to know about the requirements.
In order to qualify for .aq you would need to have some sort of "physical presence" (not necessarily permanent). That means unless you are a government and have a base there or conduct research activities then I believe you are simply not eligible. I also remember another peculiarity in that no whois service is available for .aq.
You can contact them anyway and try your luck, but I doubt the rules have changed meanwhile :emba:
To my knowledge there are a dozen or so of active .aq sites.
Obviously it's not for everyone :worried: