Out of curiosity, if I were to use another compiler, such as g++ from dev-cpp, to compile and link the dlls for foobar components, would I have any problems using that component in foobar? I recall reading somewhere that using different compilers could cause issues with other programs--for example, compiling Firefox using the GNU compiler would break compatibiliy with plugins--but I've never confirmed this.

The GNU C++ compiler is not compatible with the Microsoft compiler on the ABI (Application Binary Interface) level; even different versions of the GNU compiler produce incompatible binaries, because they changed the ABI. Since Dev-C++ uses the MinGW port of GCC, you will not be able to create working foobar2000 components with it (unless you feel like porting the foobar2000 SDK to pure C first, which won't be fun or easy).

There might be a way, if you can change the compiler that Dev-C++ uses: you could then grab a free version of Microsoft's compiler from their website and use that.