Why did I wrote it?
Because there isn't such program available for Linux, until now.
When I write documents, sometimes I want to use special characters like an E-circumflex.
To do that, I have to write a program that prints all ASCII characters to stdout and copy the character to clipboard.
I'm like the Windows' Character Map, because it's easy and fast to use.
So I wrote one by myself for Linux.
Note: Gnome Character Map will also work in other Unix platforms like FreeBSD, Solaris, etc. because Gnome Character Map's source code is completely ANSI and POSIX compliant.
It should be possible to compile it in Win32 without any changes, but I'm not sure.