LinEd is, as you probably saw on the home page, a line-based text editor. That means that instead of editing an entire file, as you would do in a normal text editor, you only edit certain lines in the file. This makes it less powerful, but it can be much faster if there is a small change you want to make in a large file. It can also be faster for other things, but working out when to use it as opposed to, say, VIM is left as an exercise for the end user.
It is written in Perl, so if your system can run Perl it can probably run LinEd. One caveat is that it currently requires the POSIX standard module for maximum funcationality, so non-POSIX-compliant systems (such as Windows) will miss out slightly. It isn't crippling, though, and we plan to implement a work-around (if it works) using the nonstandard, but easily accessible Term::ReadKey module (available from CPAN.org) so that Windows users don't miss out. Aren't we nice?
For the interested, the only thing that currently requires POSIX-compliancy is autoentering, that is when you enter a command that isn't in the least bit ambiguous (to be less vague: if you press a letter key) you won't need to press enter to confirm it. One disadvantage of this is that you currently can't erase the first character of each command, but that will hopefully go soon.
LinEd was started because Weirdofreak was annoyed at the lack of quick and easy ways to correct his frequent mistakes, which he never noticed until after saving the file. So he put off his other projects (which were far less interesting anyway) and started to write one. Really, it seemed like a good idea at the time.