"TV shows on DVD" has a page where you can keep up to date with news about the Young Indiana Jones series DVDs. An article from last year reports that extensive special features are planned, namely educational documentaries about the characters and periods.
The DVDs will probably be released to coincide with Indiana Jones 4, due in 2007, according to IMDB. Meanwhile, you can buy it in VHS format from Amazon. A rare laserdisc box set of the entire series is being sold on eBay, starting at USD $260 and shipping worldwide from Hong Kong.