How to get english language word database?

You can find what you need on infochimps.org.

They have a list of 350,000 simple (ie non-compound) words available for free download.

Word List - 350,000+ Simple English Words

Regarding other languages, you might want to poke around on Wiktionary. Here is a link to all the database backups - the information isnt organized so likely but if they have a language, you can download the data in SQL format.

WordNet database might be helpful. I once worked on a Firefox add-on which deals with words and all kinds of simple to complicated associations between them and stuff. Looks like WordNet will be very much useful to you.

Here it is in MySQL format. And this one (web-archived link) uses Wordnet v3.0 data, rather than the older Wordnet 2.0 data.