Inserting a bit of text without using the template

I have a bit of text that I want to insert on several pages, but I have no idea how to do it. These pages already have a set theme, and this text is basically a software license. It can’t be added to the theme because this text will be displayed inside the stuff displayed by the_content().

I figured adding something like “php get_license();” (the text file containing the HTML is license.php, with the appropriate PHP code, of course!) in the entry’s text would work, but of course, it didn’t.

I’m probably missing something really obvious here. If you can help out this clueless person, please do. Thanks. ??