This is a high-priority for us. By focusing on web-standards and avoiding proprietary plugins we're pretty confident that the content will be future-proof.
Something that could help is perhaps a choice that examples should work in (e.g.) Firefox recent.x on ubuntu, then provide a VM and archived version of firefox. Put it on a platform that archives things with C/LOCKSS and get a doi, then although you're not expecting people to use it on a daily basis, it'd cover several "worst case" kind of scenarios.
Of course that's not completely permanent, but would perhaps provide some more safety.
Of course that's not completely permanent, but would perhaps provide some more safety.