This has been asked before but the answers all seems a bit dated (or I missed the magic post), so:
What options do I have to generate the uuid for my objects? For now I just edited it by hand, changing a single char from what it was in the object I used as a starting point. Somehow I get the feeling that this might not be the correct solution.
A command-line option on linux would be perfect 
From what I understand, if you use Axolotis own object editor to edit and dave the object, Axoloti handles the UUID stuff.
Before I started using Axos own editor, I used Textwrangler and when using Textwrangler I had to do the UUID change manunally. After I started using Axos own object editor I did not encounter this problem.
What are you using to edit objects?
I'm using axolotis object editor. But for the initial copy-existing-object-to-my-version I just copied the object from the command line. I seem to remember that after this axoloti complained about the uuid, so I just edited the .axo file with emacs and changed one character in the uuid by hand.
What's the best way to do this; develop an object based on an existing object?
the best way is to save your object in your user library from within the axolotl object editor, that way the uuid will be generated for you. copy to library is the command you are looking for. you can also save your already modified object with "copy to library" again and it will generate a new uuid.
Hi, could you tell me how I can "copy to library" the new object?
I edited my new object with an external editor and saved with the axo extension; everything works fine but I haven't the UUID
thanks in advance
AFAIK you first need to start editing an existing object by right clicking -> "edit object definition"
A new editor window opens where you select File->Copy To Library
Pick the home library and enter a name.