When configuring an application in LM, the LicenceProductID and RenewalProductID fields can usually be left blank. They are for use when integrating an ecommerce module. An ecommerce module can ask LM to issue a licence for a particular product. The Module passes LM a productID with the request, LM looks up the app in question against the Licence Product ID field and issues the licence. Licence renewals work similarly.
See section 7.5 Using the e-commerce API in the Licence Master user manual for more information.
Btw, if in doubt about the purpose of a field, check the help popup on the page (click on the question mark icons) - it should give you some guidance.
Regarding the spelling question, it's a difference between UK and US English! Welcome to the world of localization :-) You can edit the labels in question using the DNN language editor if you want to.