Agile should be used as a flexible methodology, for sure some parts of it can be used. Your working place doesn't matters. If you work remotely you can catch up with the team by doing video call or using other work collaboration tools. Now days remotely you can even do pair programming, agile won't be a problem.
Agile can be used on an open source project but what methodology is used depends on project owner/sponsor/manager. So if you are contributing to someone others opens source project, probably it would be hard to influence on how the project is managed.
Is Agile suitable for project usually depends on multiple factors but remote work is not one of them.