I don't even think it needs to be source code. It could just be the binaries. Then the "store operator" would be in charge of packaging. Some of the Loki installers have been redone for newer versions of Linux. That kind of approach could be done wholesale.
A universal frontend could be done for the old games by someone like Linux Game Publishing as a proof of concept. They could even throw in some old apps too.
Distribution support would be driven by demand of course.