This thread reminds me of a project that's already in full swing. However,
it is released under GPL which is at odds with the BSD license and may
limit its usability for the Dreamcast port.

Excerpts from http://www.pocketlinux.com/devcenter/about.xsl

<---SNIP--->
Kaffe - our Open Source Java implementation developed with embedded
devices in mind - it enables PocketLinux to provide a uniform programming
engine on any device, regardless of hardware.

XML - used to represent all data in PocketLinux whether it is the
configuration database, the incoming email and news feeds, or the way
applications look on the screen. This enables maximal interoperation
between devices.

<---SNIP--->
PocketLinux can run on any hardware, and because we use XML and Java we
can run the same applications anywhere... on the web, on a cellphone,
anywhere. Right now PocketLinux is available on two PDA devices - the
"Helio", a low-cost PDA made by VTech, and the "iPaq", a high-end PDA from
Compaq. In both cases we replace the shipped software with the PocketLinux
platform and, once the core software is installed, any new XML and/or Java
software runs on the platform unchanged, even though the devices are
radically different.