It took me a couple of nights of hacking to get RXTX compiled and installed successfully on a PPC PowerBook G4 running Ubuntu 9.04 Jaunty. Ultimately, I was successful building from the rxtx-2.2pre2 source. Here's what I did.
Next, I edited the "configure" to remove "-source 1.3 -target 1.3" both times it appears.
The Zsystem.java file has moved from src/System.java to src/gnu/io/Zsystem.java. After finding its new home, I applied the edit suggested by fab, removing
else if (mode == J2SE_LOG_MODE)
Finally, in src/RawImp.c, the code I removed looks a bit different. I removed these lines:
#ifndef __APPLE__ /* dima */
#endif /* PPC */
#endif /* dima */
Now, when I first attempted to compile, it failed with this error
./src/I2CImp.c:135: error: 'UTS_RELEASE' undeclared (first use in this function)
Some further research pointed to a workaround solution, as noted here: (sorry the board will not let me post an active line because I'm a n00b, you'll have to reconstruct yourself) mailman.qbang.org / pipermail / rxtx / 2009-February / 4371059.html
In my case, I used "uname -r" to get my release info, and edited /usr/include/linux/version.h to include the following final line
#define UTS_RELEASE "2.6.28-6-powerpc"
At this point, I was able to successfully make and install
sudo make install
And Arduino 0017 now runs without complaints.