I will renew the domain name only one last time.
You will be able to access SmartPropoPlus site by it's direct URL http://smartpropoplus.sourceforge.net
SmartPropoPlus is Free and will stay so. You can always download the program from SourceForge free hosting.
SmartPropoPlus is an Open Source project. You You can always download the code from GitHub free hosting.
However, SmartPropoPlus is not maintained anymore and will probably be replaced with newer and better applications.