If your DSL is statically typed then I recommend that you have a look at the Mono CLR; it's compatible with the ECMA-335 standard and the IR (CIL) is well docum

If your DSL is statically typed then I recommend that you have a look at the Mono CLR; it's compatible with the ECMA-335 standard and the IR (CIL) is well documented, even with secondary literature. If your DSL is dynamically typed I recommend LuaJIT; the bytecode is lean and documented (not as good as CIL though). LuaJIT also works well with statically typed languages, but Mono is faster in the latter case. Even if it was originally built for Lua any compiler can generate LuaJIT bytecode. Both approaches are lean (Mono about 8 MB, LuaJIT about 1 MB, much leaner and less complex than e.g. LLVM), general purpose, available on many platforms (especially the ones you're mentioning) and work well (see e.g. https://github.com/rochus-keller/Oberon/ https://github.com/rochus-keller/Oberon/ and https://github.com/rochus-keller/Som/ https://github.com/rochus-keller/Som/).