I have a NiosII IP core full license ver 5.0. Am I stuck using the legacy 5.0 tools (5.0 versions of NiosII IDE and SOPC builder which are probably restricted to winXP or Linux), OR can I use this full license with newer versions of the tools?
Welcome to INTEL forum. The license is backward compatible. It will support any version released prior to maintenance expiry date even if it's expired. In you case, this license will support legacy 5.0 tools and below.