They're reasonable signs that the JavaScript is non-trivial, not restrictions. You can write a program that uses them and release it under a free software license and LibreJS will run it.

Here's a good example of a trivial JavaScript program.

<a href="#" onclick="javascript:alert('hello world')">click me</a>

For any non-trivial JavaScript programs, a free software license is required if you want it to be run by LibreJS -- a program designed to block any nonfree software from running on your computer inside a web browser.