Yanoff by Matthias Jordan is a GPL'd newsreader with a GPL'd conduit available. Supports online or offline reading and posting.
Yanoff Java Conduit by Jan-Pascal van Best " is a Java-based conduit for the Yanoff news reader... The conduit connects to the specified NNTP servers during HotSync and installs new articles on your device. It also posts and mails articles you "saved in Yanoff. You can specify newsrc files for every news server, so that articles you read on you PC news reader are not transferred to the handheld."
New Yanoff by SonLight Software "is a closed-source fork of the original NNTP newsreader client, GPL Yanoff. With New Yanoff, the premier portable newsreader
, you can read your favorite internet newsgroups ANY TIME, ANYWHERE. New Yanoff is the most customizable, mature, and fully-featured Palm OS newsreader available as well as a very capable, basic SMTP email client. It consists of two different programs: Yanoff+ and (free) Yanoff-."
PPCNewz by The Byte Foundry "is a freeware offline newsreader for the PocketPC. It uses PCNewz (included in the download) to download messages to the PC, which are then synchronized with the PocketPC, either then or later (when the PocketPC is placed in the cradle)."
Grendel, part of the Mozilla project, does mail and news.
JNews (sourceforge) "Usenet news reader written in Java using a custom NNTP class and a MySQL backend to store article information."
MobileNews "allows you to follow Usenet newsgroups and discussions using mobile devices, particularly mobile phones."
NewsBro by Michael Bergknoff " is a news reader application that uses your web browser as its user interface. By using the browser interface to access news groups NewsBro integrates news group reading with web browsing. With NewsBro you can set bookmarks for news groups just like any other web page."
NJN (the Nehelenia Java newsreader) by Alex Taylor "is, or will be, a Usenet news client implemented in 100% pure Java. NJN is loosely modelled after the superb OS/2 newsreader, ProNews/2, but is much less complex."
SkateNews by Apostle1 is described as a simple threaded newsreader written in Java for Linux.
WebReader: a java based newsreader by Fractal Images.