Hi,
This is my little BASIC compiler for Linux and Windows. It is free (as in freedom). It's quite well documented. It uses NASM as a backend by default, but can be configured to use FASM by changing one character in a config file. I chose to make NASM the default because NASM is also free. The compiler is written in Haskell and C.
https://sourceforge.net/projects/bubblebasic/Make sure you get the latest version. The latest .zip file has binaries for Linux and Windows and you can install by running a simple bash/batch script. One thing I neglected to put in the documentation is that .zip files don't seem to preserve the Linux "executable" bit, so before you run install-linux.sh, run these commands:
chmod +x bubble-basic
chmod +x libspiritlevel.so
chmod +x install-linux.sh
Enjoy,
Clockwork Dev Studio