What is it?Heartbleed is a vulnerability in recent (2012-2014) versions of the OpenSSL library that allows malicious attackers to steal data from webservers. See
this XKCD comic for details:
Is the Glade affected?No. If the website doesn't use https, then it's not affected. If the website doesn't use OpenSSL, it's not affected. If the version of OpenSSL is before early 2012, it's not affected.
What should I do if I think I'm compromised?If a website does have a vulnerable version of OpenSSL, hopefully they've updated their software by now to a fixed version. If so, changing your password is your best course of action. If they haven't, don't go to the website until they do.
That's all I got for now. I'm sure others can add more info and discourse.