Without sounding too loaded with all technical jargons let me tell you ALP or Access Linux Platform is Access's strategy to revive the good old Palm OS, so at the core its a Linux OS but they have wrapped Palm interface on top of it so it looks quite familiar to old Palm OS which came with Zire, Treo and Tungsten from Palm.
If you want to develop applications for soon to be launched ALP phones like Samsung i800, you can develop applications for old Palm OS 5 and it should run find on the new phones as well. You can also develop Java applications like you do for other mobile phones and they should run fine on it as well. You also have choice of writing web 2.0 applications to be run on their NetFront browser, but the best choice for developing a new application is developing a native application for ALP.
You can develop native ALP applications using ALP Development Suite which is available on their Developer Portal - http://accessdevnet.com/. ALP Development Suite includes:
- A complete Eclipse-based set of development tools
- The Glade 3 Interface Editor for GTK Apps
- The ACCESS Linux Platform Simulator which runs on the Linux™ desktop and provides seamless application debugging
- A Compilation Toolchain: gcc, linker and gdb
- The VirtualPhone Tool which simulates a carrier network for telephony applications
- Scratchbox, which enables command-line development and cross-compilation for ARM device targets
- Headers and libraries
- How-To Documentation and an Integrated API Reference