It's a standard security practice to limit the permissions to the minimum necessary. Because of this, software is installed in directories without write permissions for normal user. Configuration and any other files that the user needs to write aren't stored in the same directory than the software but in a user local config dir.
This patch makes glest.log, glestuser.ini, glestuserkeys.ini and screenshots to be stored in the local directory. It's only implemented for Linux since I don't know the details of Windows, but I'm sure Windows offers an API to find the user local folder ("C:\Documents and Settings\[username]\Local Settings\Application Data" in Windows XP, "C:\Users\[username]\AppData" in Vista/7 and perhaps "HD:Users:[username]:Library:Application Support" in Mac OS X?)
To implement it in other OSes the "getUserConfigDir()" just needs some ifdefs for each platform.