Only users having User License as salesforce can create articles is it true?.Can people having Salesforce Platform license create articles? or people with other User License create articles?
Administration of Knowledge requires an add-on Knowledge license. This Knowledge administration permission is provisioned on the user's records, via a checkbox. I believe that this permission can be granted to platform license holders but you would need to check with your Salesforce account executive.
Salesforce Knowledge comes free in read-only mode so it's already available to all users. However, should you wish to add information to it, you need to purchase author licenses. Thus, your editorial and QA teams would need additional paid licenses in order to create, review and maintain your support data.