There are a number of complications that maybe caused by the period or comma, which is why I think the developer prevented in the first place.

By allowing user to input period (“.”) character, the calculator is no longer type safe. This means that users may input an invalid number that produces an error when calculated.

For example: 17..1 + 44.1.9.

So, accepting the period will need more advanced masked input such as those available in WebInput of UXMaskedInput.

However, if you feel that you can manage the errors, I can suggest you to make a minor modification to the Calculator.js file in EditorPack1. Please find and modify the code shown in the following snippet code.

Original code:

...
if (!((48<=e.keyCode && e.keyCode<=57) || (96<=e.keyCode && e.keyCode<=105) || e.keyCode == 115 || e.keyCode==32 || e.keyCode==8 || e.keyCode==37 || e.keyCode==39))
{
	e.cancelBubble = true;
	e.returnValue = false;
}
...

Modified to:

...
if (!((48 <= e.keyCode && e.keyCode <= 57) || (96 <= e.keyCode && e.keyCode <= 105) || e.keyCode == 115 || e.keyCode == 32 || e.keyCode == 8 || e.keyCode == 37 || e.keyCode == 39 || e.keyCode == 110 || e.keyCode == 190)) {
	e.cancelBubble = true;
	e.returnValue = false;
}
...

keyCode for the period character, 110 and 190, is added into the "if" conditional code.

Hope this helps.