to establish a new "search engine" you cant score with some free scripts, because you always as good (or bad) as the search engine you relay on. http://www.exalead.de (change language here) one looks nice, but im not sure if this much stuff arround the results is really good. google and msn are just more plain and usefull, thats why i prefer them. i reckon if you start to overload your search-engine script with lots of adsense as on all this mfa-sites you wont get much friends or returning visitors.
I own a ppc search and you can generate a lot of money from this type of viral script. I think I paid like $10USD off eBay a year ago that’s including first month of hosting and now I’m making at least $500 a month. www.paid-results.com
If you can build specialized search engine, like, only search links within single industry or a country, it will be fine. Otherwise no use.
I bought one of these on ebay last month - NorthStarSearch - Like most sites and scripts that I have bought in the past I have found that it needs a lot of tinkering witch I have yet to finish.
Many Meta search engine scripts are available and can be easy to set up! I took the long route and set up one with webspider, database and it is slowing growing in size.