Sharing Programs
You can share Fractal Science Kit fractal programs you have written with your friends by simply exporting the programs to a file and giving the file to your friends. They will open the file and copy/paste the programs they wish to use into their library of programs. There are several areas to watch out for however.
If your programs use macros in your My Macros library, you will need to distribute these as well and your friends will need to add these macros to their My Macros library too. One can think of this as a benefit since they will also get to use your macros outside the context of your programs, but it can cause problems if your macro names collide with existing macros in their library. It is also tedious to determine which macros are required by a given set of programs, and probably easier to simply export your whole My Macros library to a file. However, this increases the chances your friends will have problems merging your macros with theirs. To minimize these problems, I recommend that you use distinctive macro names which will reduce the chance of collision down the road. If you are planning to distribute your macros to many people on multiple occasions, you may want to place your initials in front of your macro names or devise some other naming convention to make your macros easy to merge into theirs.
Another place you can go wrong is where you reference the files associated with Textures, DataFile statements, and L-System programs. Clearly, these files must be distributed with any program that uses them but it is also important to locate these files in the Fractal Science Kit folder My Files. If you do not plan to distribute your programs, this is less important, yet still recommended. You can organize your files by placing them in folders that you create under the My Files folder (e.g., My Textures, My Data Files, My L-Systems). Files located in the hierarchy under My Files will be referenced using a relative path to the file rather than a fully qualified path which is highly specific to your machine.
Sharing Fractal Files
The issues associated with sharing fractal files are the same as with sharing programs. The programs referenced by your fractal files, however, are not an issue since they are embedded within the fractal files themselves.
Sharing your Home folder
You can avoid all of these problems (assuming you have taken the recommendation above about storing Textures, DataFile statements, and L-System programs in the Fractal Science Kit folder My Files) by sending your friends your entire Fractal Science Kit Home folder and instructing them to save it on their machine somewhere and use the Fractal Science Kit /home:<path> command line argument to name that folder. This avoids the whole issue of merging macros since they will be running with your environment (i.e., your macros, programs, support files, etc.) not theirs. See Changing the path to your home folder for details.