If the first item in the form is readonly calling setFocusOnFirstActive() does not skip it. It is still an active item since it is visible, but who needs a focus on a readonly item?
Your example does not work in either Firefox, Chrome or IE. It sets focus on the first item of the form which is readonly. In IE (version 11.0.9600.16428) you can even see it since IE puts a blinking cursor (vertical line) in front of the “inp1” value. In all three, hitting tab key brings the focus to the second field.
Here is a simple modified required for getFirstActive() function. In the if condition:
if (k && this._idIndex[this._indexId[q]].enabled) return this._indexId[q];
an additional check is required:
&& !this.isReadonly(this._indexId[q])