Links

X11-Basic Applications:

• GPS-earth A graphical frontend for GPS-receivers.

• TTCar A LED speedometer that displays interesting data like active sats, speed, acceleration, altitude and compass in a nostalgic way.
• TTMoto displays your current speed in large text across the top half of the screen, making it easy to read whilst riding a motorcycle.

Articles about X11-Basic:

• BASIC programming with Unix Article in LunuxFocus by John Perr
• Intérpretes y compiladores de BASIC A comparison of different BASIC solutions for linux (spanish) by Marcos Cruz
• X11 Basic: Μια απλή BASIC βασισμένη στην GFA BASIC του Atari ST (Ubuntistas Issue 16, p.24-29) A tutorial about X11-Basic (greek) by του Χρήστου Τζιώτζη

Other BASIC languages

• Stbasic, bwbasic, quickbasic to C translator for UNIX/Linux This is rather outdated code, but this might be a basis, if you want to write your own BASIC interpreter or compiler.