If you copy the data-worksheet-ro-id, RU000nE7 in this case, and create a URL from it like http://lastcalc.com/RU000nE7, anyone that visits that URL will get a copy of that worksheet that they can edit without affecting the original. I know it's messy, I'm working on it :-)
The reason this kind of thing isn't properly exposed in the UI yet is that I need to figure out how worksheets can be shared, and "published" (allowing other people to "import" functions you've defined). This will require user accounts and I haven't begun that infrastructure yet. When worksheets are published, there also needs to be some kind of peer-review.
So much to do, but I'm making rapid progress. Thanks for your feedback, this is invaluable, please keep it coming :-)
Since you keep the complete spreadsheet on the server side it would be great to have a possibility to share the spreadsheet using Facebook / Twitter or just the plain URL without copying it from the address bar.
In addition it could be nice to lock the spreadsheet so that when you share it nobody can modify it anymore.
While thinking about this, what about forking a spreadsheet?