You can download Baxter for PPC and x86 from five different places. In addition, the Baxter add-on SDK is available and so is the source for the QueryCLAmp application.

Mirror 1: Chicago (ABiSoft) x86 R5 PPC R5
Mirror 2: Chicago (ABiSoft mirror) x86 R5 PPC R5
Mirror 3: United Kingdom (courtesy of Andrew Edward McCall of H2O Software) x86 R5 PPC R5
Mirror 4: Milwaukee, Wisconsin (courtesy of Brian Luft) x86 R5 PPC R5
Mirror 5: Germany (courtesy of Brian Luft) x86 R5 PPC R5

At this time there is unfortunately no version of Baxter for BeOS R4.5. Baxter X is still available for x86 and PPC.