Using the REPL application you can generate the necessary ingredients to create licenses
first create a new license:
L3J> $ newLicense
this creates a license without owner
now, generate the keys:
L3J> $ generateKeys public=public.key private=private.key
this saves the keys to 2 files
sign the license with the private key:
L3J> $ sign
save the license to a binary file
L3J> $ saveLicense format=BINARY license.bin
The license file can now be verified using the public key.
In case you want to sign the license later, you must skip the sign step above and use the private key file to sign the license at a later time