Is there any way to prevent a program from being distributed via transfer between two calculators? Is there some sort of code that can be embedded in the program that makes it untransferrable or unusable after it has been transferred?
No, TI-Basic does not have access to the calculator's hardware. It is probably possible to do something like that in assembly, but that would require in-depth knowledge of the calculator.
Welcome to TI-Basic Developer!
So, did you find the protection page helpful?
In my opinion, all programs should remain unlocked, and allowed to spread freely throughout the world as people send them to person to person. And so other less experienced programmers can learn from our programs.
Actually I find that if you lock your program and then put an activation code on it, you can prevent it from being used by anyone who does not come to you and let you input the code. This would only work locally as you would have to use the same password for each copy of the program, meaning you would have to put it in yourself or else word would spread and anyone could use your program.
If you get Doors CS 6, you can unlock any basic program.
There are several assembly programs you can use to unlock TI-Basic programs: CalcSys, MirageOS*, Z-DOS, Program Tools, just to name a few.
*This only works if the TI-Basic program shows up.
encrypt the code whit weird stuff like seq(, T and cumsum(