In what country are you located?
In the US, a certain amount of legal protection can be acquired by mailing a copy of the program in a sealed letter through the US Postal Service to *yourself* and then saving the unopened letter/package in case of legal disputes. The postmark from the USPS is generally accepted in court as basic date of discovery, invention, copywrite, etc. This technique has been used in the publishing business for years.
However, in the US, patents and other rights can apply to the "look and feel" of an application. I am not sure how to proceed in that area. There are probably other steps required to reserve your rights internationally.
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The trouble with doing something right the first time is that noboby appreciates how difficult it was.
- Steven Wright