It told me I needed gnustep-core-devel and libmozjs-dev, so I ran
aptitude install gnustep-core-devel libmozjs-dev
Started to compile (with a few warnings), but then I got
Compiling file src/Core/Scripting/OOScript.m ...
Compiling file src/Core/Scripting/OOJSScript.m ...
src/Core/Scripting/OOJSScript.m: In function ‘-[OOJSScript initWithPath:properties:context:]’:
src/Core/Scripting/OOJSScript.m:184: warning: pointer type mismatch in conditional expression
make: *** [oolite.all.objc-program.variables] Error 2
make: Leaving directory `/home/user/software_products/oolite/trunk'
make: *** [build] Error 2
Edited GNUmakefile, changed -ljs to -lmozjs as Shade suggested, and removed ../oolite_1.69* in case this was preventing my change from taking effect. Same error.
I found a libjs.a in the package libjs0-dev, so I installed it and changed -lmozjs back to -ljs, but that didn't seem to help either.
libmozjs-dev in Etch is version 126.96.36.199-pre070702 Is this not backwards compatible with 1.7?