This site has been around the internet for over 12 years. Is it popular? No. Is it big? Yes. And growing every day. Really. I make a point to update, add, or otherwise do something on the site every day. Even when I am sick I got some updating done. So it came from Matt, with a ton of work all the time. No other site like it has as many features. New ones are being added all the time.
Everywhere, really. I would say mostly the Internet such as the famous WikiPedia. They have lists upon lists. I used one list of all games that work with the PlayStation Move. This allowed me to update about 100 games that use or require the PS Move with an icon that looks good. Many parts have been user submitted, mostly on version 1 of the site.
Post in the forums. I read them, so posting there I can make your changes soon. Some day I plan to open editing to all users, but I have put so much time into the site I am afraid of rouge people posting spam or whatnot. If you submit images, be sure there are no watermarks from other sites on them!
A few ways. Submit your changes in the forums. Donate. This helps cover hosting costs. Link to us or directly to a post on other sites so that search engines like us more.
PHP. MariaDB for the database. Framework by UserSpice
I found a duplicate. I get this a lot. Sometimes it just the same title, just from another country or language. Sometimes its the same name but a different console. Sometimes one is a bootleg/counterfeit. It all gets tracked! Sometimes one is three screw and the other is five in the case of NES cartridges. If you really found a dupe, post about it in the forum.
I cant find anything with search. The site search is not as good as Google. Games may be in the database as "2" but you searched for "II". It sees it as two different things. Skip the word "The". Use less words, then limit it using the "Narrow by Platform" drop down. Really cant find it? Post in the forums and I will try to help or add the game. If it needs to be added, include as much detail as you can.