[thasmin]

Almost all of the relevant code is in wp-content/db.php. It's using Wordpress's hook that lets you use custom code to connect to the database. The code is rewriting MySQL flavored SQL into SQLite flavored SQL which is impressive but potentially flaky. I'd want to see how well it handles SQL from popular plugins before I'd start building a website using this.

[2000UltraDeluxe]

If you want a simple blog with little extras, I'd expect this plugin to work just fine.

The predecessor plugin, SQLite Integration, was fairly stable with most other plugins, but plugins trying to do unconventional stuff or hit the DB directly would refuse to work. The main issue was that the plugin author stopped updating the plugin, while newer versions of WordPress didn't suppport it.