I want to apply for my first "real" (read: non-freelance) Ruby on Rails job.

I've built several apps already. My best work (also the most logically complicated app) was for a freelance client, and I'd like to show it to potential employers.

Only problem is: it isn't online anymore. And I've lost touch with the client. How can I include this work in my portfolio?

About the app: It's a Facebook game. The client's business idea for this app was not the best. It was never going to make any money. I think it was kind of a vanity side project for him. The logo and graphics are nice-looking, though, and were designed by the client.

I've actually spent a lot of time recently recoding most of the app, and adding a full test suite. I want to showcase the BDD / TDD skills I've acquired.

I'm not very familiar with the etiquette (/law?) concerning this situation.

Can I just put my new version of the app up at a free Heroku URL (perhaps with a "credits" section, where I credit the ideas and graphic designs to my former client)?

NOTE: Again, this is just to show potential employers. I am not trying to market the app as my idea, or attract any users.

Can I put some or all of the code on GitHub? What if I don't put the code up publicly, but merely send a tarball to potential employers?

Do I need to ask permission from my former client (and what if he says no)?

The last thing I want to do is get in any legal trouble, or offend people I'm trying get a job from. But I believe that my work and experience on this app are my highest recommendation for getting a job.